This paper presents a novel actuator system combining a twisted string actuator (TSA) with a winch mechanism. Relative to traditional hydraulic and pneumatic systems in robotics, TSAs are compact and lightweight but face limitations in stroke length and force-transmission ratios. Our integrated TSA-winch system overcomes these constraints by providing variable transmission ratios through dynamic adjustment. It increases actuator stroke by winching instead of overtwisting, and it improves force output by twisting. The design features a rotating turret that houses a winch, which is mounted on a bevel gear assembly driven by a through-hole drive shaft. Mathematical models are developed for the combined displacement and velocity control of this system. Experimental validation demonstrates the actuator's ability to achieve a wide range of transmission ratios and precise movement control. We present performance data on movement precision and generated forces, discussing the results in the context of existing literature. This research contributes to the development of more versatile and efficient actuation systems for advanced robotic applications and improved automation solutions.

Reversible morphing wings, capable of exchanging the direction of the leading and trailing edge, improve the feasibility of stopped-rotor aerial vehicles and thereby expand aerial robotics capabilities. Despite the potential benefits of reversible morphing wings, few designs exist and most do not consider the coupled aerodynamic and structural effects of the introduced morphing mechanisms. We report a six-bar linkage-inspired reversible morphing wing design that is compliant, yet structurally rigid against aerodynamic loading. Compared to alternative methods for reversing airfoil direction, the developed wing increases the maximum aerodynamic performance by 50%, while also yielding a non-zero efficiency at 0° angle of attack. The proposed linkage system derives rigidity by strategically eliminating degrees of freedom upon actuation. To validate the linkage theory of rigidity, the full wing is studied under one-way fluid-structural interaction simulations. Furthermore, we demonstrate how constrained optimization can be applied to improve the aerodynamic efficiency of these wings subject to the constraints of a six-bar linkage system.

Robotic endoscopes have the potential to help endoscopists position tools during procedures, to propel the endoscope to the desired position, to automate functions and to prevent perforations during procedures. This paper outlines the modular architecture for a continuum robotic endoscope with multiple bending segments along the length of the endoscope. Each of the segments is modular, containing a set of actuation motors that drive short cables in the continuum segments. Each modular segment of the robot is 15 mm in diameter, can turn 180 degrees and has a turning speed ranging from 35 to 250 degrees per second. The robot is composed of seven of these modular segments, has 14 degrees of freedom, is 0.91 m long and has a mass of 157 grams. The implementation for the mechanical, electrical, and software design is described and the robotic endoscope bending motions are sensed, simulated and controlled using kinematic models. Lastly, path planning trajectories of the endoscope segments are designed and coordinated to help propel the robot forward in an uncoiling motion and in a follow-the-leader fashion along a path that emulates simplified turns in a colon. We show that the robotic endoscope is able to exert less force on the walls of the colon emulation path, enable automated insertion into the patient, and execute colon wall avoidance and linear scanning motions not available in conventional endoscopes.

A modular system of small digital sensors and generators that includes a user interface with a graphical display and auditory feedback is being developed to address the limitations associated with measuring various aspects of human performance using bulky and often incompatible wired sensors and associated instrumentation. The initiative is called MICA (Measurement, Instrumentation, Control and Analysis) has entailed developing a high data rate, low latency wireless protocol. Optimized for real-time measurement and control, the protocol has been developed to link a network of sensors and generators to a central data acquisition system. The goal in designing MICA was simplicity and modularity at minimum cost without sacrificing instrumentation quality. The performance of the MICA sensor system is described in the context of measuring electrophysiological variables from active humans and the motion of objects under human control.

Angular displacement sensing and contact force sensing in robotic surgery is important for finding the conformation of the tool and for closed loop control. Current techniques for measuring large deflections, such as electromagnetic tracking, involve bulky external reference equipment. This paper discusses the design, dynamic modeling, and kinematic simulation of a compact two-axis bend sensor constructed from layers of carbon black filled polyurethane for determining the bending angle of a cable-driven continuum robotic endoscope. The sensor is flexible (10% strain), compact, and does not require external reference equipment. The sensor is able to bend in 180 degrees in all directions, produces two-axis outputs that are linear up to 120 degrees of bending and has a response time less than 9 ms. This paper explores the use of the sensor for controlling the tip position of a robotic endoscope and detecting external forces. The design outlined in this paper has many possible applications in robotic endoscopes, surgical tools, snake-like robots and soft material robotics.

We present the design of a novel direct-drive linear permanent magnet synchronous motor with a high continuous-duty force-to-mass ratio. We use an analytical electromagnetic model to find optimal dimensions for a new magnet configuration, comprising nested tubular Halbach arrays. We further use the analytical model to map out the design space for these motors, and investigate possible designs for motors with muscle-like force production. We then describe the design of a 100 g-scale motor based on the optimization, with water cooling and a lightweight structure. Experimental results suggest that this motor is capable of over 140 N/kg continuous force production, and demonstrate that it can be used for positioning at over 1 m/s and with 40 g acceleration unloaded.

Conducting polymer actuators such as polypyrrole can generate stresses over 10 times larger than skeletal muscle and have typical repeatable strains between 1% and 12%, making them potential candidates for lightweight, low-cost, robotic applications. Polypyrrole linear actuators under closed loop control have not been previously reported. Here we report the open and closed loop performance of polypyrrole linear contractile actuators evaluated at pre-loaded stresses of 1 MPa to 3 MPa. A standard PI control scheme driving a potentiostat was implemented in conjunction with positioning feedback from a DC/DC linear variable differential transformer (LVDT). A dynamic positioning range of 3400 is reported, with a positioning resolution of 125 nm (0.001% strain) and a maximum repeatable displacement of 427 microns (3.6% strain). The open loop frequency response of actuator strain shows characteristics of a first-order low pass filter with a log gain versus log frequency slope near -1 for frequencies tested between 0.05 Hz to 2 Hz. The closed loop frequency response of actuator strain when tracking a sinusoidal set-point signal of 0.5% strain shows characteristics of a first order system with one zero, with a corner frequency near 0.08 Hz and an operating bandwidth up to 1 Hz. Step responses at various controller output maximum voltages show a reduction in contractile response times by a factor of four, where higher voltages yield faster contractile responses.

A series of biorobotic fins has been developed based on the pectoral fin of the bluegill sunfish. These robotic fins model physical properties of the biological fin, and execute kinematics derived from sunfish motions that were identified to be most responsible for thrust. When the physical properties of the robotic fin are tuned appropriately to operating conditions, the robotic fin, like the sunfish, produces positive thrust throughout the entire fin beat. Due to having many degrees of freedom, these fins can be used to generate and control forces for propulsion and maneuvering.

The emerging fields of nanosciences and nanoengineering will provide the ability to work at the molecular level to create larger structures with new molecular organization. This understanding and control over the fundamental building blocks of all physical entities will lead to new emerging opportunities in factory automation. Although research in this field is very active, little has been done toward increasing the throughput rate, a factor that will be critically important in future nanofactories. An approach for the implementation of scaleable and high-throughput nanofactories based on a fleet of miniature autonomous robots capable of operations at the atomic-scale is described.

The transmission system of the Utah/MIT Dextrous Hand (UMDH) is investigated theoretically and experimentally. It is shown that the friction of the routing pulleys is not negligible and should be considered in the force control of the UMDH. In the frequency range of the pneumatic actuators (80 Hz), tendons act like springs and the first mode of the tendons is above that frequency range.>

A microrobot having two high-performance parallel drive limbs has been developed for manipulation, surgery, and dynamic mechanical testing of very small objects such as single living cells. The end-points of each limb move in overlapping spherical workspaces of 1 mm diameter with minimum open- and closed-loop movements of 1 nm and 10 nm, respectively. With optimal nonlinear model-based controllers the limbs can move at up to 2 m/s relative to each other. A variety of end effectors, including ferroelectric polymer microgrippers, may be attached to the limbs to permit cell manipulation. A 3D laser vision system with resolution of 50 to 100 nm has been developed to provide the microrobot with volume images containing magnitude, phase, polarization, and special information. A macro version of the microrobot has been built to enable force-reflecting teleoperation of the microrobot. The telemicrorobot system permits both microscopic objects and continuum models to be felt. A high-performance parallel computer has been designed to meet the substantial computational and control requirements of the system.>