Presented in this paper is a single actuator mechanism for airfoil shape morphing. The said mechanism is designed as a linkage array that is driven by one actuator to provide multiple output points along the entire airfoil shape. This mechanism consists of two components, namely the shape adaptation linkage (SAL) and the connector linkage. Each connector is made up of a passive camber connector (PCC) or an active camber connector (ACC). The PCC conditions the output of an SAL while the ACC serves to create the camber morphing effect. The design method is proposed with three steps: Camber Mapping, Shape Adaptation Linkage Synthesis, and Connector Synthesis. The proposed method has been applied to design a number of NACA airfoils with camber morphing to demonstrate the effectiveness.

While 6-leg, 6 DOF parallel robots offer advantages over serial mechanisms in many applications, they suffer from mobility limitation pertaining to both the maximum extension of links and link interference. The latter of these can be mitigated by a reduction of the number of links in the mechanism. The end-effector’s degrees of freedom are maintained by adding controllable degrees of freedom to the remaining legs. This paper presents a prototype of a previously proposed 3-leg, 6-DOF parallel robot. A measure of its workspace is also shown and compared to that of a similarly sized 6-leg parallel mechanism. Analysis of partial derivatives of Cartesian points with respect to joint angles is also explored to give a metric of expected performance in different regions of workspace.

Currently, harmonic drives are the primary speed reducer for robotic applications where a high reduction in a small package is required. Cycloidal drives are an alternative option for high reduction, small package, use-cases with the advantage of a higher specific torque and the ability to customize and integrate the drive for the application. These compact style cycloidal drives have been well studied in theory and simulation for their performance, but very little data is available on their actual performance over time. This paper presents experimental data on performance of a cycloidal drive designed for a Lunar or Martian rover application. Burn-in time efficiency curves and torque/speed efficiency profiles are computed after running the drive through 129k output cycles (7.6M input cycles) over the course of 300+ hours of testing. The study finds that substantial burn-in time may be required for steady-state performance, but peak efficiencies of 81% can be achieved. Also, the efficiency is shown to be dependent on the torque through the actuator. This work demonstrates a customized cycloidal drive in a space application that is comparable to a harmonic drive in efficiency performance, with a 2x increase in specific torque, suggesting the application of cycloidal drives could grow tremendously in robotic designs.

The classical approach to decrease the energy consumption of high-speed robots is by lowering the moving elements mass in order to have a lightweight structure. Even if this allows reducing the energy consumed, the lightweight architecture affects the robot stiffness, worsening the accuracy of the mechanism. Recently, variable stiffness actuators (VSAs) have been used in order to reduce the energy consumption of high-speed pick-and-place robots. The idea is to smartly tune online the stiffness of VSA springs so that the robot is put in near a resonance mode, thus considerably decreasing the energy consumption during fast pseudo-periodic pick-and-place motions. However, the serial configuration of springs and motors in the VSA leads to uncontrolled robot deflections at high-speeds and, thus, to a poor positioning accuracy of its end-effector. In order to avoid these drawbacks and to increase the energy efficiency while ensuring the accuracy, this paper proposes the use of parallel arrangement of variable stiffness springs (VSS) and motors, combined with an energy-based optimal trajectory planner. The VSS are used as energy storage for carrying out the reduction of the energy consumption and their parallel configuration with the motors ensure the load balancing at high-speed without losing the accuracy of the robot. Simulations of the suggested approach on a five-bar mechanism are performed and show the increase on energy efficiency.

Industrial robots need motors with high-precision positioning, large torque output, and small size. However, the conventional motors combined with reducers tend to be large. To solve the problem, we proposed the motor integrated with reducer that could output reduced rotation directly by using the strain wave gearing system. The proposed motor is thought to have advantages not only in downsizing but also in high load-supporting capacity and high stiffness because of the simultaneous engagement of three gear pairs. In this paper, we derive the theoretical input-output relation in the proposed motor with a focus on the deformation of the elastic gear in the motor. The result gives the pushing force of the linear actuators at an arbitrary output rotation angle of the motor. We conduct the experiments to clarify the optimal input pattern for the accurate rotation by using the prototype of the proposed motor. Through the observation and measurement, the optimal input pattern is suggested.

Series Elastic Actuators (SEA) are one of the most widely studied compliant actuators in anthropomorphic robots and prostheses. However, due to the nature of its unique configuration, an unavoidable trade-off has to be made between compliance and bandwidth performance. In this paper, we show that by adopting a hypocycloid mechanism in rotary actuator designs, compliance and high force control bandwidth can be achieved at the same time, while reaping all the benefits of energy storage and shock absorption characteristics of mechanical springs.

This study proposes and examines a novel approach to generate peristaltic locomotion gait in a segmented origami robot. Specifically, we demonstrate how to harness elastic multi-stability embedded in a soft origami skeleton to create an earthworm-like locomotion. Origami is attractive for building soft robots because it can exhibit the essential compliance and reduce the part count. Most importantly, it can work as an actuation mechanism. Moreover, embedding multi-stability into an origami skeleton allows it to remain in any of the stable states and switch between different states via a series of jumps. In this paper, we use two serially connected bistable Kresling segments, each featuring a generalized crease pattern design and a foldable anchoring mechanism, to develop a driving module for crawling soft robot. Multi-stability analysis of this dual-segment module reveals a four-phase actuation cycle, which is then used to generate the peristaltic gait. Instead of controlling the segment deformations individually like in earthworm and other crawling robots; we only control the total length of our driving module. This approach can significantly reduce the total number of actuators needed for locomotion and simplify the control requirements. The purpose of this paper is to combine the best features of multi-stable mechanisms and origami to advance the state of art of earthworm inspired crawling soft robot. Our results demonstrate the potential of using multi-stable origami mechanisms to generate locomotion gaits without the need of complex controllers.

This paper presents trajectory planning methods for a kinematically redundant parallel mechanism. The architecture of the mechanism is similar to the well-known Gough-Stewart platform and it retains its advantages, i.e., the members connecting the base to the moving platform are only subjected to tensile/compressive loads. The kinematic redundancy is exploited to avoid singularities and extend the rotational workspace. The architecture is described and the associated kinematic relationships are presented. Solutions for the inverse kinematics are given, as well as strategies to take into account the limitations of the mechanism such as mechanical interferences and velocity limits of the actuators while controlling the redundant degrees of freedom.

This paper presents a trajectory planning approach and an analysis of the geometric design parameters for a planar cable-suspended translational parallel robot based on a parallelogram cable loop. The cable robot produces purely translational movements in a planar workspace. Furthermore, this special architecture only requires two actuators which makes it fully actuated. From the dynamic model of the robot, general algebraic inequalities are obtained that ensure that the cables remain taut. A general elliptic trajectory is then defined and substituted into the algebraic inequalities to obtain conditions on the geometrical design parameters that ensure that the cables are always in tension. In addition, a special trajectory-specific oscillation frequency emerges and enables the end-effector to dynamically move beyond the boundaries of the static workspace, thus expanding the workspace of the mechanism. Finally, a kinematic sensitivity index is studied in order to assess the influence of the parallelogram structure on the rotational stability of the mechanism.

Soft robots are a specific type of robots that are made of elastomeric materials. A specific type of soft actuators (soft robots) are called fiber-reinforced soft actuators. Effective parameters in the motion of fiber-reinforced soft actuators are cross-section area, thickness of the actuator, number of threads wrapped around the actuator, angle of threads, and if the fiber is wrapped one-way or two-way. Some of these parameters are already studied by researchers in the field. In this research, the aim is to investigate the effect of the angle of the fiber on the motion of a semi-cylindrical fiber-reinforced soft actuator with an inextensible layer attached to its flat surface. This paper studies the behavior analysis of the actuator, which is modeled in a finite element software. The behavior of the actuator in terms of bending is then studied by changing the angle of the fiber wrapped around the outer surface of the actuator. Results show that the bending behavior of the actuator highly depends on the fiber angle. Simulation results are then validated with experiment. The results presented in this paper provides an instruction on how one can improve or optimize the bending workspace of the actuator as needed.

The balancing capabilities of a legged system can be influenced by several properties of the system itself, for instance, the strength of joint motors in a robot or muscle strength in living systems. In this work, the changes in the balancing capabilities of a legged system are evaluated as the joint actuator torque limits of the system change. The legged system is modeled with an inverted pendulum model with an actuated ankle and a finite foot size. The effect of variations of the ankle torque limits on the system balance stability is quantified through the local properties of Lagrange multipliers in optimization theory and are validated through numerical experiments. With the proposed method, the information on the balance stability boundary of a legged system is used to predict the balance stability characteristics of the system with altered joint torque limits, hence providing quantifiable guidelines to the design of such systems.

Rotating beams are quite common in rotating machinery e.g. fans of compressors in an airplane. This paper presents the experimental, hybrid, structural vibration control of flexible structures to enhance the vibration behavior of rotating beams. Smart materials have been used as sensors as well as actuators. Passive constrained layer damping (PCLD) treatment is combined with stressed layer damping technique to enhance the damping characteristics of the flexible beam. To further enhance the damping parameters, a closed form robust feedback controller is applied to reduce the broadband structural vibrations of the rotating beam. The feed forward controller is designed by combing with the feedback controller using a pattern search based optimization technique. The hybrid controller enhances the performance of the closed loop system. Experiments have been conducted to validate the effectiveness of the presented technique.

Curved bistable beams subjected to transverse loading may exhibit latching, namely remain in their buckled state under zero force. Under such circumstances, an opposite force is required for snapping-back (release) of the beam to its initial configuration. For an electrostatically actuated beam, two electrodes located at either side of the beam may therefore be required for bidirectional actuation. In this study, a new snapping and release procedures, are considered. The approach involves the preloading of the beam using an electrostatic force in the direction opposite to the beam desired movement, followed by a sudden release of the voltage. We show, by means of a reduced order (RO) model, resulting from the Galerkin decomposition, that such an actuation paradigm can not only be used to release a beam from its latched position, but can also create a snap-through response at a significantly low voltage.

In order to create shape memory alloy (SMA) bimorph microactuators with high-precision features, a novel fabrication process combined with electron beam (E-beam) evaporation, lift-off resist and isotropic XeF 2 dry etching method was developed. To examine the effect of E-beam deposition and annealing process on nitinol (NiTi) characteristics, the NiTi thin film samples with different deposition rate and overflow conditions during annealing process were investigated. With the characterizations using scanning electron microscope and x-ray diffraction, the results indicated that low E-beam deposition rate and argon employed annealing process could benefit the formation of NiTi crystalline structure. Besides, SMA bimorph microactuators with high-precision features as small as 5 microns were successfully fabricated. Furthermore, the thermomechanical performance was experimentally verified and compared with finite element analysis simulation results.

This paper reports on the design, fabrication, and characterization of non-interdigitated comb drive actuators in Silicon-on-Insulator (SOI) wafers, using a single mask surface microma-chining process. The response of the actuator is analyzed numerically and experimentally. The results show at the fundamental frequency; it behaves as a longitudinal comb drive actuator. At a higher frequency, it exhibits a high-quality factor which is appropriate for sensor applications.

A scanning force microscope combining commercial AFM probes, printed circuit boards, and electrostatic actuation and detection is proposed and demonstrated. The electrostatic actuator is formed by the AFM probe and a fixed trace on a PCB. It is driven by a biased harmonic voltage with a frequency close to the probe’s resonant frequency. The separation distance between the probe tip and the specimen surface is managed to perform tapping mode scanning. A lock-in amplifier measures the second harmonic of the actuator current as the sense signal in an open-loop scheme. Preliminary results produced by the current’s magnitude and phase resemble the specimen’s topography.

Linear actuation is a basic need in robotized manipulation of surgical instruments, that must comply with a challenging environment in terms of safety, compactness and now often compatibility with imaging modalities like CT or MRI. In this paper, we focus on needle manipulation for interventional radiology. We propose a needle driver, i.e. a linear actuator for needle insertion, based on the inchworm principle combined with pneumatic energy. Our first contribution is to propose, model and implement the device using a so-called auxetic structure. Its use increases achievable displacement under pressure and provides sufficient off-axis stiffness to use the actuator without additional guidance. Simplified modeling is introduced for the actuator synthesis. Our second contribution is to implement the actuator with multimaterial additive manufacturing combining rigid and flexible materials to increase compactness. As a third contribution, initial assessment of component sterilization and compatibility with X-ray and MRI imaging modalities is presented.

Variable stiffness mechanisms have a wide range of applications in the field of human-robot interactions such as rehabilitation robotics, prosthesis and industrial robotics due to their ability to comply with the human limb stiffness in an unstructured environment. This paper presents the analysis of a single degree of freedom variable stiffness actuator based on nonlinear force interactions between permanent magnets and its effect on the natural frequency of the system. In the proposed mechanism, variable stiffness is achieved by modifying the separation between magnets. The main goal here is to achieve a desired cutoff frequency by varying the stiffness of the system to filter out the involuntary movement of upper limb during physical human-robot interactions. Moreover, due to the spring-like non-contact force interactions between magnets, this mechanism can prevent the exchange of high impact forces between the robot and human.

This paper presents a study on the energy utilization of planar automation mechanisms that operate with controlled moves. Designers of factory automation for pick & place tasks often select multiple degree-of-freedom robotic devices. With multiple degrees-of-freedom, task flexibility is available, but many operations require little or no flexibility. The majority of research on the energy usage of these robot devices for pick & place tasks focuses on path planning. The study presented in this paper explores the energy savings in using low degree-of-freedom devices and the influence of design parameter selection. Energy predictor equations are developed and confirmed through experimentation. Various positioning mechanisms of differing dimensions are studied for trends in energy utilization. Lastly, an actuator control strategy is proposed for further reducing energy requirements. The study concludes that energy usage can be substantially decreased in pick & place applications by reducing the degrees of freedom of the device, implementing a prudent mechanism architecture, ideally selecting mechanism dimensions and optimally controlling the actuator(s).

This paper deals with dynamic analysis of three methods for the slider in mechanisms. Three methods are introduced under three conditions (the influence of friction force is considered, the slider’s center of mass is not coincide with the hinge point, the slider and its guide have rotation motion). The dynamic analyses of the crank slider mechanism and the flying shear mechanism are given as examples by a developed software based on Visual C++ environment, and application scope of the three methods is concluded at the end of the paper. These results are useful for analyzing and designing mechanisms with sliders, such as choosing suitable slider materials or actuators.