ICRA 2017 论文列表

Locomotion of water beetles have been widely studied in biology owing to their remarkable swimming skills. Here, we investigated the coordination between the two pairs of legs to achieve steady swimming with novel hair-like appendages. Some design considerations and a fabrication of the hair-like appendages, which can passively adjust their projected area to obtain net thrust, are proposed. As do water beetles in nature, the coordination between the two pairs of legs were considered to achieve steady swimming without jerky motion by varying the beating frequency and phase of the legs. To verify the functionality of the hair-like appendages and their coordinations, six different types of appendages were fabricated, and two robots (one with single pair and the other with two pairs of legs) were built. Locomotion of the robots were compared through experiments, and steady swimming was achievable by properly coordinating the two-pairs of legs without sacrificing the swmming speed.

An effective robotic wrist represents a key enabling element in robotic manipulation, especially in prosthetics. In this paper, we propose an under-actuated wrist system, which is also adaptable and allows to implement different under-actuation schemes. Our approach leverages upon the idea of soft synergies — in particular the design method of adaptive synergies — as it derives from the field of robot hand design. First we introduce the design principle and its implementation and function in a configurable test bench prototype, which can be used to demonstrate the feasibility of our idea. Furthermore, we report on results from preliminary experiments with humans, aiming to identify the most probable wrist pose during the pre-grasp phase in activities of daily living. Based on these outcomes, we calibrate our wrist prototype accordingly and demonstrate its effectiveness to accomplish grasping and manipulation tasks.

Brain-computer interface (BCI) systems can translate the human mind into control commands, which makes it feasible to improve the life quality of physically challenged people. However, in real-life situations, it is still difficult for users to utilize robots to provide basic services with BCI systems. We aimed to propose a BCI-based system with a visual servo module to operate a service robot. We recorded single-channel steady-state visual evoked potentials (SSVEP) as input signals for the BCI system of this study. The visual stimuli for inducing SSVEP were modulated at seven different frequencies with the sampled sinusoidal method. Correspondingly, this SSVEP-based BCI system can generate seven control commands for the operation of the service robot, which can provide three fundamental services: mobility, manipulation, and delivery. The visual servo module was established to reduce the burden of users and accelerate service procedures. To evaluate the performance of this system, subjects were recruited to participate in the experiments. All the participants succeed in operating the robot to provide the basic services. According to the experimental results, this SSVEP-based BCI system that incorporates the visual servo module can be effectively used to operate service robots with reduced number of channels and increased ability to perform multiple tasks.

This paper presents a new variable stiffness actuator (VSA) based on a structure-controlled method: controlling the mechanical structure of the actuator by rotating four flexure hinges. The VSA possesses a property that the output position and stiffness are independently controlled. This is realized by a serial arrangement of a principle driving motor, a small stiffness variation motor and a novel variable stiffness mechanism (VSM). The VSM consists of four combined notch flexure hinge frames, each of which contains an inner rotary flexure shaft and outer stationary hinge housing. The stiffness is adjusted by rotating the inner flexure shaft to change the second moment of area. Its value is independent to the VSA output angle when the flexure rotational angle is fixed. The working principle of this VSA is elaborated and the optimization mechanical design of the VSM is presented. A prototype has been implemented and its primary characteristic test results validate the design features.

This paper introduces the SCCA Hand, a five motor robot hand developed using a minimalist design approach that focused on grasping abilities in real-world environments. Notable features include a novel bidirectional tendon underactuated finger design that biases actuator force toward finger flexion, an additive manufactured monocoque steel construction that enabled enhanced feature density and a low parts count, low grasp impedance by means of series elastic actuation, shock absorption for protection from impacts, and anthropomorphic speed, strength, and size. In addition to a description of its design, experimental characterizations of speed and force capabilities as well as demonstrated achievement of eight canonical grasps and postures are provided.

Modern passive ankle-foot prostheses do not exhibit appropriate biomechanics during walking, and are unable to adjust their mechanics for other mobility tasks, such as stair traversal or quiet standing. In this paper, we introduce a quasi-passive ankle-foot prosthesis that addresses these challenges; the ankle has a customizable, nonlinear torque-angle curve, and the overall stiffness can be varied continuously between mobility tasks. The variation in mechanics is accomplished by integrating two mechanisms: a cam-based transmission, in which rotation of the ankle joint causes deflection of a leaf spring, and an active sliding support beneath the leaf spring, which can modify the spring's effective stiffness. In addition to introducing the design, we present the mathematics to calculate the cam profile for any arbitrary torque-angle curve, and experimentally characterize the system for a desired curve based on human walking. Lastly, we demonstrate the full range of stiffness levels available and stiffness transition time.

This paper presents the design of a novel variable stiffness gripper with two parallel fingers (jaws). Compliance of the system is generated by using permanent magnets as the nonlinear springs. Based on the presented design, the position and stiffness level of the fingers can be adjusted simultaneously by changing the air gap between the magnets. The modeling of magnetic repulsion force and stiffness are presented and verified experimentally. An experiment is also conducted to demonstrate the functionality of the gripper to improve safety when a fragile object was grasped and the gripper collided with an obstacle.

This paper presents the design of a flexure-based precision positioning micro-motion stage system with constant output force. The stage mechanism is devised using folded leaf flexure (FLF) to achieve positive-stiffness structure. Bistable beams are employed to design negative-stiffness structure by using their buckling characteristics. Two bistable beams and two FLFs are combined together as a zero-stiffness structure. Complete models of the amplifier and the zero-stiffness structure are established and verified by using finite element analysis (FEA) simulation. The structural parameters are carefully designed to guarantee the performance requirement of motion range, stiffness and driving force. A prototype stage is fabricated by 3D printing process and a series of experiments are conducted for performance testing. Experimental results show that the developed positioning stage delivers a reachable constant-force motion range of 138 μm with good motion repeatability.

Actuators for human-interactive robot systems require transparency and guaranteed safety. An actuation system is called transparent, when it is able to generate an actuation force as desired without any actuator dynamics. The requirements for the transparent actuation include high precision and large frequency bandwidth in actuation force generation, zero mechanical impedance, and so on. In this paper, a compact rotary series elastic actuator (cRSEA) is designed considering the actuation transparency and the mechanical safety; the mechanical parameters of a cRSEA are optimally selected for the controllability, the input and output torque transmissibility, and the mechanical impedance. A mechanical clutch that automatically disengages the transmission is devised such that the human is mechanically protected from an excessive actuation torque due to any possible controller malfunction or any external impact from a collision. The proposed cRSEA with a mechanical clutch is applied to develop a wearable robot for incomplete paraplegic patients. Experimental results of a manufactured cRSEA system are introduced in this paper also.

Most collaborative robots use high-power motors for a good weight-to-payload ratio, thus leading to not only an increase in manufacturing cost but also possibility of injury at a collision between a human and a robot. To maintain high-performance with low-power driving units, a spring-based counterbalance mechanism (CBM) and a robot arm based on these CBMs were developed in our previous study. In this study, a 6-DOF collaborative robot equipped with a multi-DOF CBM is proposed. A double parallelogram linkage and a slider-crank mechanism are employed for a compact and durable design of a multi-DOF CBM. Unlike the previous prototypes in which some portions of CBMs were protruded out of the robot body due to their large volume, the proposed CBMs can be embedded inside the robot links. The performance of the developed CBM and collaborative robot were verified based on simulations using dynamic simulation software. Simulation results show that the proposed CBMs can effectively reduce the joint torques required to operate the robot. This reduction in the torque enables low-power motors to be used in a collaborative robot, thus significantly improving collision safety and energy efficiency.

This paper reports on a novel 3D-printed polymeric compliant constant-force buffering gripping mechanism. The motivation of this work is to develop a buffering gripping mechanism to avoid the damage of manipulated biological object induced by excessive displacement output. The presented zero-stiffness mechanism is realized by connecting the negative-stiffness part and positive-stiffness part in parallel. The negative stiffness is obtained by a bistable buckled fixed-guided beam mechanism. Analytical modeling and simulation study are carried out before the prototype fabrication with 3D printing. Experimental results show that the proposed gripping mechanism can provide a constant output force of 780 mN in 500 μm motion range. Results also reveal that the manipulated object bears no deformation in the constant-force range, which is enabled as the excessive displacement output is buffered by the mechanism. The proposed design can be used to replace the existing combined force-displacement control strategy for fragile object manipulation.

This paper presents the mechatronic design and experimental validation of a novel powered knee-ankle orthosis for testing torque-driven rehabilitation control strategies. The modular actuator of the orthosis is designed with a torque dense motor and a custom low-ratio transmission (24:1) to provide mechanical transparency to the user, allowing them to actively contribute to their joint kinematics during gait training. The 4.88 kg orthosis utilizes frameless components and light materials, such as aluminum alloy and carbon fiber, to reduce its mass. A human subject experiment demonstrates accurate torque control with high output torque during stance and low backdrive torque during swing at fast walking speeds. This work shows that backdrivability, precise torque control, high torque output, and light weight can be achieved in a powered orthosis without the high cost and complexity of variable transmissions, clutches, and/or series elastic components.

This paper presents a novel multi-axis robotic platform for the characterization of two important neuromuscular properties of the human ankle: mechanical impedance and reflex responses. The platform is capable of producing highly accurate position perturbations up to an angular speed of 200°/s and emulating a wide range of haptic environments in two degree-of-freedom (DOF) of the ankle: dorsiflexion-plantarflexion (in the sagittal plane) and inversion-eversion (in the frontal plane). This unique feature allows us to seamlessly simulate realistic mechanical environments and to transiently perturb the ankle for the characterization of its neuromuscular properties. The position controller achieved the accuracy of 0.05° even under the loading condition (a subject of 95 kg standing on the platform). The haptic controller could successfully emulate a wide range of mechanical environments, from compliant to rigid (50-1000 Nm/rad), with an error of 2% of the commanded values. We further validated that the proposed platform could reliably estimate the stiffness of a mockup (17.8-171.0 Nm/rad) that resembles the human ankle within an error of 1.6%. Finally we demonstrated that the platform could be successfully utilized to elicit medium-latency and long-latency reflex responses of the ankle muscles. Implications for future ankle studies are discussed.

We present the design and implementation of a quadrotor tail-sitter Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicle (UAV). The VTOL UAV combines the advantage of a quadrotor, vertical take-off and landing and hovering at a stationary point, with that of a fixed-wing, efficient level flight. We describe our vehicle design with special considerations on fully autonomous operation in a real outdoor environment where the wind is present. The designed quadrotor tail-sitter UAV has insignificant vibration level and achieves stable hovering and landing performance when a cross wind is present. Wind tunnel test is conducted to characterize the full envelope aerodynamics of the aircraft, based on which a flight controller is designed, implemented and tested. MATLAB simulation is presented and shows that our vehicle can achieve a continuous transition from hover flight to level flight. Finally, both indoor and outdoor flight experiments are conducted to verify the performance of our vehicle and the designed controller.

In applications of human-robot interactions, accurate measurement of interactive forces between the human and the robot plays a significant role. Such sensors should not only be accurate and reliable, but also be soft enough to guarantee the safe and compliant human-robot interaction. In this aspect, pneumatic sensors with soft air chambers have often been utilized as a soft force measurement system. Although such a sensor system provides a good compliance and softness, however, it measures only a lumped force acting on the chamber, because the measurement of the pneumatic sensor is the pressure change in the air chamber. For the measurement of multi-dimensional interaction forces with high softness and compliance, a three-axis force measurement system is devised by arranging three air chambers in a radially symmetric pattern. Each air chamber embeds a pneumatic sensor, and the pressure changes in the three air chambers are measured in order to distinguish the direction of the applied force. By decoupling the sensor signals from the three pneumatic sensors, the three-dimensional force components can be calculated accurately. Consequently, the proposed sensor system is able to measure the three-axis forces while maintaining the great softness and compliance provided by the soft air chambers. The design, the fabrication method, and the verification of the proposed method are introduced in this paper.

Aerial robotic platforms are an increasingly sought-after solution for a variety of sensing, monitoring, and transportation challenges. However, as invaluable as unmanned aerial vehicles (UAVs) have been for these applications, fixed-wing and multi-rotor systems each have individual limitations. Fixed-wing UAVs are generally capable of high-altitude surveillance and long flight times, while quad-rotors are most effective when used for their maneuverability and close-quarters surveying. This paper improves upon the prototypes discussed in [1] by creating a series of three next-generation prototypes to isolate the aspects of solar powered fixed-wing flight, quad-rotor flight, and transformation modes of the SUAV:Q platform. Improvements to the transformation mechanism, airframe design, variable pitch propulsion system, and custom-designed power electronics are presented along with validation of the designs through empirical testing.

This paper describes the Transformable HOvering Rotorcraft (THOR), a prototype Unmanned Aerial Vehicle (UAV) that explores a novel approach in combining the range and speed of a horizontal flying platform with the hovering and maneuverability of a rotor-wing. This is achieved by integrating a tailless flying wing configuration with a single-axis rotor, or monocopter. By maintaining full utilization of all aerodynamic surfaces and propulsion sources in both flight modes, this method represents the most structurally efficient approach to achieving a cruising mode and a hovering mode on the same frame. Using a dual servo and motor configuration, we propose an under-actuated system that is able to achieve controllability in 4 degrees of freedom while in its horizontal cruising mode and in 5 degrees of freedom while in its hovering mode. In both indoor and outdoor experiments, the UAV is able to transition between either flight modes seamlessly and repeatedly without the need for any additional mechanisms and actuators.

This paper proposes a Magneto Rheological linear clutch for use in human safe robotic applications. The force transmitted to the links of the robot must be precisely controlled for any manipulator if it has to be operated safely alongside humans. The traditional approaches to this problem is using various compliant actuating schemes like Series Elastic Actuators, Joint Torque Control etc. Research on the usage of smart materials that change their properties on application of electrical or magnetic fields for human safe robots have gained momentum recently. Studies on the feasibility of Magneto-Rheological actuators has been done already. This paper introduces a MR clutch which can control the force transmitted by a linear actuator. The electromechanical model of the linear clutch has been developed, implemented in hardware, and tested using a prototype one Degree of Freedom arm. The design of the clutch is detailed and the performance is characterized thorough a series of experiments. The results suggest that the linear clutch serves well for the precise force control of a linear actuator.

This paper presents an inchworm inspired soft robot composed of the soft body, the front foot as well as the back foot. Compared to the traditional inchworm-type robot consisting of rigid components, the driven mode for the soft robot is more simple. The soft robot inspired by the inchworm has higher locomotion efficiency than the other bionic soft robot. The main idea of this paper is to imitate the “Ω” motion shape of biology inchworm based on a silicone square tube with strain-limiting layers. Besides, each foot of the robot made through 3D printing technology together with metal sheet can produce different friction coefficients to achieve the anchor-motion movement. Then, the robot realizes an inchworm-like locomotion under certain actuation patterns. Experimental results show that the proposed robot has excellent performance.