IROS 2017 Papers

In this paper, we design and build a power line inspection robot capable of hybrid operation modes. Specifically, the developed robot is able to land on the overhead ground wire (OGW) and to move as the climbing robot. When to negotiate obstacles, it can vertically take off the wire and fly over the obstacles as the unmanned aerial vehicle (UAV). A customized trumpet-shaped undercarriage is used to guarantee that the robot can land and move safely. With the aid of a swingable 2D Laser Range Finder (LRF), the robot can not only determine whether there are obstacles but also detect the position and orientation of the OGW, making it suitable for automatic inspection of power lines. The outdoor experimental results1 demonstrate the effectiveness of the robot in landing and obstacle negotiation. In addition, the average power consumption of the robot is much lower than that of traditional flying robots for power line inspection.

Applying differential drive robots to cooperative systems introduces difficulties regarding the maneuverability of the cooperative system. These difficulties are caused by the sliding constraint of the plain wheels typically used by differential drive robots and mainly affects the turning capability of the cooperative system. This can be a problem when a cooperative system traverses narrow spaces or manipulates large objects. Conversely, differential drive robots are simple to design and control for single robot tasks. To enable differential drive robots to participate in multi-robot cooperative systems, a novel wheel capable of switching between plain and omni-wheel modes is proposed. By selecting the appropriate mode, differential drive robots would be able to work in both single and multi-robot tasks seamlessly without adding complex control to the single robot case or degrading the maneuverability of the cooperative system. As an initial step, the kinematic modeling and the prototype of the wheel is presented together with tests using two differential drive robots implemented with the proposed wheel.

Developing a high physical performance robotic manipulation platform with considerable power density, strength and resilience is not a trivial task and frequently leads to heavy and bulky systems unable to meet the application requirements, i.e. such robots should have human body size compatibility to work in infrastructures designed for humans. In this work we present a new high performance human size and weight compatible bi-manual manipulation platform that demonstrates notable physical strength and power capabilities. To attain this performance, design features including custom high performance elastic drives and robust light weight structure principles were considered resulting in large payload to robot mass ratio that is greater than 1.5 for short time heavy payloads. The design principles and mechanics of the upper body bi-manual robot are presented providing details on the solutions adopted for the various mechatronics components. The performance of the system actuation and the strength capacity of the overall platform is verified through the execution of heavy payload motion and impact experiments.

Hovering flight is one of the valuable capabilities for unmanned aerial vehicles (UAVs) to perform various missions. It is easily attainable by rotary-wing aircrafts such as a helicopter and multirotor. This flight maneuver, however, remains a significant challenge to a flapping wing micro air vehicle (FWMAV). This paper aims to regulate attitude angles of a FWMAV and maintain an altitude during hovering. For this task, we model dynamic equations of FWMAV to analyze the stability of longitudinal dynamics under the influence of tail wings. In order to examine the effect of the flapping wings on the fuselage, we carry out measurements on the power train. We develop a FWMAV with two pairs of main flapping wings and tail wings, to achieve stable hovering flight. For autonomous control, PID controllers are designed and onboard sensors are used; 9-degree of freedom (DoF) IMU is for attitude regulation and barometer is for an altitude control. For estimating an altitude, we also apply processing filter. Experimental results show that our strategy can accomplish and sustain autonomous hovering of a FWMAV.

Bladder cancer constitutes the thirteenth most common cause of cancer death worldwide. Transurethral resection of bladder tumors (TURBT) is the established treatment procedure of non-muscle invasive bladder cancer. However, current techniques for this procedure represent several inadequacies such as inaccurate resection of tumors and high recurrence rates due to the lack of dexterity and limited instrumentation. In this paper we proposed a concept to improve the efficiency of this procedure. Starting from the anatomic challenges, the design and fabrication procedure of a double arm surgical manipulator made of nitinol was presented. A new actuation concept was introduced which enables a surgeon to facilitate ten degrees of freedom simultaneously. Finally, in-vitro experiments regarding workspace and functionality were conducted to evaluate the developed system. The workspace experiments showed that the entire surface of the bladder can be reached by the manipulator. We also demonstrated that with the developed system, basic tasks such as pick-and-place and circular path marking can be performed.

In this paper, we propose a design method for the mechanism of a robotic arm suitable for a multicopter. The motion of an arm attached to a multicopter can possibly disturb the multicopter attitude. Our aim is to suppress this attitude disturbance by mechanical methods. In the proposed design method, the arm has the following features for suppressing the disturbance of the multicopter attitude. 1. The robotic arm can adjust its center of gravity (COG). 2. In the simplified model, the sum of the angular momentum of the rotating parts constituting the robot arm is equal to zero. These features can compensate for both the displacement of the COG of the arm and the counter torque generated from rotating parts, which cause the disturbance to the multicopter attitude. Since the disturbance of the multicopter attitude can be suppressed mechanically, the robotic arm does not require a special flight control law. In other words, this robotic arm has the advantage of being attached to a multicopter using a common, off-the-shelf, multipurpose flight controller. Furthermore, we discuss the mass distribution, power transmission method, and the moment of inertia of rotating parts, such as the speed reducer, motor, and arm. Additionally, we fabricate a prototype robotic arm with four joints and three degrees of freedom (DOFs), based on the proposed design method. Finally, the experiments showed that the robotic arm suppressed the disturbance of the multicopter attitude caused by the arm motion.

As a part of our research on several different types of Giacometti robots, a 20-m-long, considerably light, and simple robot arm, referred to as the Giacometti arm, is developed in this study. Even though the Giacometti arm is not suitable for precise positioning, rapid motion, and high load capacity, which are the aspects most conventional robots focus on, it is designed for extremely specific purposes such as the inspection of otherwise unreachable regions using a small camera at the arm's tip. In addition, it is designed to be essentially safe even if it falls down or hits an object. This aspect is realized using helium-filled balloon bodies and thin pneumatic muscles. In this paper, we designed new Giacometti arm which is 20-m-long, weighs 940 g, and has 20 degrees of freedom. To realize this long arm, we derived a kinematic model of the 20-m-long Giacometti arm, factoring in the air resistance. We verified the model using the arm, and its utility was confirmed at a mock-up facility.

This paper presents the design and evaluation of a new sensorized underactuated self-adaptive finger. Our design incorporates a two degrees-of-freedom (DOF) parallel based underactuated mechanism with an embedded load cell for contact force measurement and a trimmer potentiometer to acquire the joint variables. Integration of the sensors leads to tactile feedback fidelity without compromising the finger size and complexity which results in efficient and robust functionality. The particular rounded shape of the distal phalanx and high equilibrium position enable the finger to deliver both precision and power grasps. The effectiveness of our design is verified theoretically and through experimental results demonstrating its shape adaptability, and tactile capability.

The closer distance between robots and human partners in the same space makes compliant robots essential in these days. While torque sensor based impedance control scheme suffers from insufficient bandwidth, musculoskeletal systems can achieve similar ability with smaller resources by using mechanically guaranteed dynamics. In this study, inspired by active stiffness mechanism of biological muscle, we developed a variable stiffness actuator which can realize precise joint stiffness without torque sensor based feedback control. The actuator consists of two antagonistically allocated DC motors with a variable radius gear transmission mechanism. The equilibrium position and joint stiffness can be independently controlled adjusting the activation level of motors by feedforward control. Theoretically predicted stiffness is realized well. In this paper, the design, functional principle and control of the actuator are introduced with analytical investigation.

Today, collaborative robots are often taught new tasks through “teaching by demonstration” techniques rather than manual programming. This works well for many tasks; however, some tasks like precise tight-fitting insertions can be hard to recreate through exact position replays because they also involve forces and are highly affected by the robot's repeatability and the position of the object in the hand. As of yet there is no way to automatically detect when procedures to reduce position uncertainty should be used. In this paper, we present a new way to automatically detect insertion tasks during impedance control-based trajectory teaching. This is accomplished by recording the forces and torques applied by the operator and inputting these signals to a convolutional neural network. The convolutional neural network is used to extract important features of the spatio-temporal forces and torque signals for distinguishing insertion tasks. Eventually, this method could help robots understand the tasks they are taught at a higher level. They will not only be capable of a position-time replay of the task, but will also recognize the best strategy to apply in order to accomplish the task (in this case insertion). Our method was tested on data obtained from 886 experiments that were conducted on eight different in-hand objects. Results show that we can distinguish insertion tasks from pick-and-place tasks with an average accuracy of 82%.

Fiber Reinforced Elastomeric Enclosures (FREEs) are fundamental building blocks of pneumatic soft robots, with McKibben muscles as common examples. When a system of FREEs are arranged in a planar configuration, they undergo large bending deformations due to internal loads and moments. This paper models the bending behavior of FREEs using a modified three-spring Pseudo-Rigid Body (PRB) model, which is commonly used to capture large bending behavior of flexures. The springs of the PRB model are shown to effectively capture the axial and bending stiffness of contracting FREEs, while an internal force accounts for actuation due to internal pressurization. An optimization process is carried out to fit the PRB model parameters with the experimental response curve of different FREEs with varying length to diameter ratio and fiber angles. Unlike conventional models applied to compliant mechanisms, the model parameters are shown to depend on fluid pressure. The PRB model is used to demonstrate and analyze a pennate arrangement of contracting FREEs that exhibit variable gear ratio behavior. The pennate FREEs can serve as building blocks for the design of soft robots.

SLAM is a fundamental problem in robotics that can be solved by a set of algorithms that are known to have large computational complexity. GraphSLAM contains a rapidly growing system of equations which are often solved by sparse evaluation techniques. This paper proposes a technique to evaluate sparse equations on an FPGA by restricting the maximum amount of items in the system. The implementation is done using CλaSH which allows a transformation from mathematical descriptions to a hardware design. The results show a scalable hardware design that can be used to solve small and large systems with dynamic parallelism.

This paper focuses on the design, modelling and hovering control of a tail-sitter with single thrust-vectored propeller which possesses the inherent advantages of both fixed wing and rotary wing unmanned aerial vehicles (UAVs). The developed tail-sitter requires only the same number of actuators as a normal fixed wing aircraft and achieves attitude control through deflections of the thrust-vectored propeller and ailerons. Thrust vectoring is realized by mounting a simple gimbal mechanism beneath the propeller motor. Both the thrust vector model and aerodynamics model are established, which leads to a complete nonlinear model of the tail-sitter in hovering state. Quaternion is applied for attitude description to avoid the singularity problem and improve computation efficiency. Through reasonable assumptions, a simplified model of the tail-sitter is obtained, based on which a backstepping controller is designed using the Lyapunov stability theory. Experimental results are presented to demonstrate the effectiveness of the proposed control scheme.

Inspired by natural earthworm locomotion behavior and segmental muscle motion mechanism, this paper presents our recently developed compliant modular earthwormlike robot with the novel segmental muscle-mimetic design unit that is capable of efficiently mimicking earthworms' segmental muscle contraction and extension functions. The new class of segmental muscle-mimetic design unit relies on the curvature of scissor mechanisms that can be extended and contracted smoothly through controlled servo motors. The paper starts reviewing natural earthworm locomotion behavior, details the bio-inspired concept and design of both the segmental muscle-mimetic unit and the multi-segment earthworm-like robot prototype, and then presents the robot's locomotion models and analysis of the locomotion efficiency of the robot. Simulation and experimental results validate that both the design and the prototyped multi-segment earthworm-like robot have the excellent performance such as its muscle-like contractions behavior, peristaltic locomotion behavior, and highly competitive moving speed.

Powered ankle-foot prostheses must provide high power and torque while satisfying stringent size and weight requirements. Previous works have focused on improving the prosthesis torque/weight ratio with novel actuation systems such as series and parallel elastic actuators, clutchable leverages, and pneumatic artificial muscles. In this paper, we propose an alternative design approach to minimize the prosthesis size and weight, while improving torque generation and electrical efficiency, based on a polycentric kinematic chain. The proposed approach is implemented on a novel powered polycentric ankle prosthesis (p2Ankle). Kinematics and mechatronic design are presented together with bench-top testing. Preliminary validation in standing and walking is conducted with an able-bodied user using a bypass orthosis.

This paper presents a novel robotic hand design that aims at producing a realistic human-robot handshake. A standard characteristic model of the human-palm compliance is developed based on human hand anatomy and an empirical study. Based on this model a realistic palm-compliance rendering is implemented. The backdrivability of the system allows a position-controlled feedback loop which renders human-like agility. An objective and a subjective experimental session, also depicted in the accompanying video, are then presented in order to validate the haptic feedback of the robotic hand in comparison to a real human handshake.

We present the conceptual design for a single degree-of-freedom shoulder assistive robot powered by a direct-drive linear electric motor. Such actuators offer high bandwidth and inherent force transparency, advantageous properties for an assistive device, but traditionally have inadequate force densities. We develop a model to describe the interaction between the robot kinematics and the actuator performance, and find the optimal actuator configuration. We also demonstrate the ability of a single design of such a device to fit a wide range of patients, and determine indicative power and mass specifications for the actuator. The resulting power and mass levels of approximately 1 kg and 130 W are well within the feasible range for a wearable device.

As the rapid development of precision medicine, in-vivo manipulation of micro/nano-scaled particles has attracted increasing attention in recent years. The collision is one of the main reasons that falls the in-vivo particle transportation fail. In this paper, we develop an in-vivo cell transportation control approach using a robotically controlled optical tweezers manipulation system, where a so-called wide-area image gradient algorithm is used to avoid collision of the transported cell with other obstacles. The controller exhibits advantages of the reduced online calculation for collision avoidance, fast response, high accuracy, as well as an ability to compensate the environmental disturbance caused by blood flow. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed controller.

In this paper, we present a novel robotic hand specifically designed for dexterous spatial manipulation. Unlike most other dexterous hand designs that attempt to mimic the kinematic structure of the human hand, the proposed mechanism instead is based on the non-anthropomorphic “hexapod” structure of the Stewart platform parallel manipulator. The hand is composed of a single “grasp” actuator connected via an underactuated differential mechanism to six prismatic actuators arranged into pairs, forming three planar, parallel mechanism fingers that replicate the kinematics of a traditional 6-degree of freedom Stewart platform when grasping an object. This configuration allows for both grasping and accurate manipulation of a range of object sizes/shapes with minimal sensing. We describe the design and fabrication of a prototype hand that incorporates these kinematics and experimentally demonstrate it performing a series of accurate translational and rotational manipulations.