IROS 2015 Papers

This paper presents a solution to the problem of decentralized control, fault detection and isolation for teams of cooperative autonomous mobile vehicles. The strategy is carried out in the discrete time domain. A local observer is used by each agent to estimate the overall state of the team. This estimate is, then, used both to compute its local control input and isolate faulty teammates, even in absence of direct communication with them. For diagnosis purposes, a set of residual vectors, each of them sensible to a fault occurring on a single vehicle, is designed and an adaptive threshold is derived in order to avoid false alarms. The approach is validated via numerical simulations involving 4 vehicles moving in formation in a 3D environment.

Efficient obstacle detection is a key requirement for safe robot navigation. We consider the operation of autonomous vehicles in structured industrial environments. In such scenarios, an usual way to perform obstacle detection is to generate an estimate of the ground and detect elements that are on the path of the vehicle, using the ground as a spatial reference. For this task, 3D occupancy grids are a well-know solution. In this work we extrapolate the concept of 3D grids by considering a discrete-continuous representation of the environment. The discrete nature lies in a 2D grid parallel to the ground whereas the continuous aspect represents the height of each cell in the grid. This framework allows for very efficient clustering, for which we also propose a novel algorithm to cluster potential obstacles. Experiments on an autonomous ground vehicle illustrate the applicability of the method.

Methods of optimizing a single trajectory are mature enough for planning in many applications. Yet such optimization methods applied to high Degree-Of-Freedom robots either consume too much time to be real-time or approximate the dynamics such that they lack physical consistency. In this paper, we present a method of precomputing optimized trajectories and compressing the information to get a compact representation of the optimal policy function. By varying the initial configuration of a robot and optimizing multiple trajectories, the controller gains knowledge about the optimal policy function. Such computation can be performed on a powerful workstation or even supercomputers instead of an onboard computer of the robot. The precomputed optimal trajectories are stored in a Single-hidden Layer Feedforward neural Network (SLFN) using Optimally Pruned Extreme Learning Machine (OP-ELM). This ensures minimal representation of the model and fast evaluation of the SLFN. We first explain our method using a simple time-optimal control problem with an analytical solution. We then demonstrate how this method can work even for high dimensional state by optimizing a foothold strategy of a full quadruped robot in simulation.

Micromanipulation tasks are usually carried out using simplistic tools such as rigid probes and needles. More sophisticated tools such as grippers are fragile, expensive and non-dexterous. This paper addresses some of the main challenges of manipulation at the micrometer scale, including robots with limited degrees of freedom, small range of available tools and open-loop control due to a lack of position sensors. This work presents a preliminary investigation into the viability of using the Direct Laser Writing and Two-Photon Polymerization microfabrication techniques for creating flexible micrometer-scale end-effectors. A novel compliant end-effector design is presented for closed-chain cooperative manipulation involving multiple micromanipulator robots. A visual servoing framework was also developed to allow the user to control the robots in a closed loop manner, with haptic feedback to help match the user's input to the speed of the robots. Characterization of the new compliant manipulator was conducted and multi-robot configurations were tested to demonstrate the flexibility, robustness and increased workspace of the new design for both 2D and 3D object manipulation tasks.

Dexterous object manipulation with robotic hands (subject to holonomic constraints) usually requires the capacity of fingertips to roll onto the object, which is very difficult to achieve with frictionless point contact model . As an alternative, deformable contact model has been considered based on hemispherical shape end-effector to yield rolling. However, it entails dexterity at the expense of dealing with normal and tangential forces, as well as more elaborated dynamic models. In this paper, a passivity-based controller is proposed for redundant robotic fingers with hemi-spherical deformable fingertips to manipulate dexterously a circular dynamic object. Redundancy and rolling are exploited to control normal and tangent contact forces to yield an optimal grasping. The optimal grasping is based on to align dynamically the normal forces applied to the object that allow its manipulation with minimum tangent forces. Stability conditions are presented to guarantee local asymptotic convergence. Finally, numerical simulations show the performance of the forces toward desired pose. This approach can be extended to objects with arbitrary shape that admit a local decomposition by a circular curvature.

In the field of medicine and biology, many studies to be related to regenerative medicine are accomplished. In particular, the purpose of helping the operation of the cells under a microscope, many research related to micro manipulation techniques with robotic technology has been proposed. In such background, we studied two finger micro hand that realized control of the sub-micro order size object. The accurate operation of the end effector against the object by the micro hand is demanded to users. To reduce the burden, we focus on making the manipulation easy. User can perform micro manipulation with rough operation by using the actuator that varies in size. Since the actuator fills space between the end effectors and the object. Then we focus on the gel that varies in size. In this paper, we evaluate the gel that varies in size. Then we propose the manipulation that take advantage of the gel.

Sub-seafloor explorations are important for biological and geological research. Sampling mud is one of the major sub-seafloor exploration procedures. The mud-including mineral resources and marine sediments are potentially valuable resources for future studies. Therefore, we propose a peristaltic-crawling-based sub-seafloor excavation robot for deep sea exploration. This robot consists of three units (propulsion, excavation and extraction units), enabling it to move freely through mud. The excavation and propulsion units are fitted with an earth auger and artificial muscles, respectively. In this paper, we verify the propulsion actuator as the first stage of robot development. First, we evaluate the performance of an oil hydraulic artificial muscle under water pressure. Next, we develop an excavation robot by incorporating a pneumatic artificial muscle into a robot and then experimentally evaluate propulsion and excavation of the robot. We confirmed that the artificial muscle appropriately performs as an actuator for the excavation robot.

Within the limbs of typical animals, there exist bi-articular muscles crossing two joints. It is known that the bi-articular muscles of the felid play an important role in the locomotion. Also the muscle-tendon complex, composed of the gastrocnemius muscle and the Achilles' tendon that cross the knee joint and the ankle joint contributes much to the movements such as running and jumping particularly. Besides, because the muscle-tendon complex has the function for absorbing shocking, it is utilized for soft landing from high places. To achieve high performance for jumping and landing motion like cats, we are developing robot legs inspired by the bi-articular muscle-tendon complex of cats. The leg consists of hip, knee and ankle joints. For the knee and ankle joints, a four-bar linkage mechanism with one elastic linkage, in which the knee joint is driven by an electric rotary motor and the ankle joint is passive, is applied. By this mechanism, basic functions of the bi-articular muscle-tendon complex of felids like cats can be realized and the performance for jumping and landing can be improved. In this paper, the new leg mechanism is described. Moreover, a prototype of a pair of the hind legs of the quadruped robot using the new mechanism has been developed. The results of jumping and landing experiments are shown to validate the effectiveness of the mechanism.

We have proposed and developed a new quadruped walking robot with a spherical shell, called “QRoSS”. QRoSS is a transformable robot that can store its legs in the spherical shell. The shell not only absorbs external forces from all directions, but also improves mobile performance because of its round shape. In rescue operations at a disaster site, carrying robots into a site is dangerous for operators because doing so may result in a second accident. If QRoSS is used, instead of carrying robots in, they are thrown in, making the operation safe and easy. We developed QRoSS-I and conducted basic experiments to verify performance which includes landing, rising and walking through a series of movements. This paper reports details of a mechanical design to perform a rotational locomotion using spherical shell and development of the prototype model of QRoSS-II. We discuss the rising motion and the rotational locomotion from the results of Basic experiments.

The main goal of this paper is to design and evaluate a spine structure which withstands various motions. The structure around the neck has a prevailing importance since it is involved in various motions of the upper half of the body. The new design method we introduce essentially shows how to design all 7 cervical vertebrae (the part of spine in the neck) in a limited space, actuated by the wires winded around the motors. Then we show the muscle arrangements around the upper half of the spine. More specifically, we make use of a so called planar muscle mechanism. An abduction experiment which requires great force around the spine is made to show its stability. Finally, we show a variable stiffness system which enables the spine to resist an impulsive force. We have tested the system in the situation of whiplash injury which is a case of extreme external forces which can occur in car crash accidents. As such we have evaluated the strength of the design and the viability of our robot to act as a human body simulator.

Falling is a common problem in the growing elderly population and fall-risk assessment systems are needed for community-based fall prevention program. In particular, gait measurements such as several-meters walk tests are carried out in community health activities. To evaluate the walking ability of the participant, it is necessary to measure foot contact positions so that the walking parameters such as stride length can be used for fall-risk assessment. However, the conventional measurement systems are difficult to install for use in community health activities because of their scale, cost and constraints of the measurement range. Therefore, we propose a gait measurement robot (GMR) using laser range sensor (LRS) for a long-distance walk tests. From the experimental results with young people, it was confirmed that the GMR could measure the both leg trajectory and the foot contact positions. However, in the case of the elderly especially, a false tracking is likely to occur due to the narrow stride. In addition, the GMR calculates the foot contact positions by analyzing the estimated position and speed of each leg. In the case of the elderly, there is a possibility that the GMR cannot detect the foot contact correctly because the walking speed is likely to be slow. In this study, we carry out the seven-meter straight walk tests with the elderly people using a stationary LRS for the advance verification of measurement in the elderly with the GMR. We verify the leg tracking and foot contact detection using a stationary LRS in the elderly compared with the video analysis.

In this paper we focus on master-slave robot hand systems that can realize non-contact sensing and intuitive mapping between human hand motion and robot hand motion. Such a master-slave robot hand system can be effective from a viewpoint of usability. However, conventional systems are not able to adapt to dynamically changing environments because they have high latency from input to output. Therefore, we developed a fast-response master-slave robot hand system using a high-speed vision system and a high-speed robot hand. The latency of the proposed system is so small that humans cannot recognize it. The motion of a human hand is obtained with high-speed non-contact 3D sensing, and this motion is mapped to a high-speed robot hand, while taking account of structural differences between the human hand and the robot hand. We confirmed the effectiveness of our proposed system through experiments.

Conventional hybrid actuators can achieve a better force/torque bandwidth than a single principle actuator without losing back-drivability. However, hybrid actuators occupy space at least equal to the sum of the volumes of two or more actuators and multiple transmissions consisting of timing belts, gears, links, tendons, or Bowden-cables. Designs in which space and structural elements of a hybrid actuator are integrated have not been sufficiently studied. This paper presents an original development work on the design of an integrated pneumatic-electromagnetic hybrid linear actuator (iPEHLA). In the integrated design, hybrid components of an air cylinder and a linear motor were arranged around a single shaft, and the pneumatic and electromagnetic actuators shared the same moving parts (i.e., piston and moving part) and internal cylindrical spaces (i.e., cylinder and stator). Consequently, space required was less than the sum of the volumes of the two actuators. To verify the feasibility of this novel integrated design, the iPEHLA was designed and prototyped by modifying parts of a commercially available pneumatic cylinder integrated with electromagnetic components. The performances of the iPEHLA under pneumatic actuation and hybrid actuation were compared with respect to a feedforward friction compensation. The experimental results demonstrated that the novel design maintained its hybrid properties.

Sewer pipes play an important role in a city's infrastructure. However, accidents have occurred in recent years due to increasingly old pipes. To prevent such accidents, there is a need to check the internal condition of pipes. Therefore, we focused on the locomotion of a robotic earthworm that is capable of running stably in a narrow space. We developed a peristalsis crawling robot with the goal of traveling 100 m through a 100A pipe. The robot is composed of six unit sections, five joints, and a head section to which the inspection camera is attached. It uses an artificial muscle operated by air pressure. In this study, we developed a new joint to reduce buckling, increase the running speed, and decrease the unit size. Further, we developed a new head section that allowed passage through a 90° elbow pipe. We evaluated the effectiveness of the new robot, and conducted running experiments in horizontal, vertical, and two types of bent pipes.

This study developed the Hanyang Exoskeleton Assistive Robot (HEXAR)-CR50 aimed at improving muscle strength of the wearer while transporting a load. The developed exoskeleton robot HEXAR-CR50 has 7 degrees of freedom (DOF) for one foot, 3-DOF for the hip joints, 1-DOF for the knee joints, and 3-DOF for the ankle joints. Through functional analysis of each human joint, two DOFs were composed of active joints using an electric motor developed in an under-actuated form with heightened efficiency. The rest of the DOFs were composed of passive or quasi-passive joints to imitate human joints. The control of the exoskeleton robot was based on the physical human-robot interaction. In order to verify the performance of the developed HEXAR-CR50, muscle activity was measured using electromyography, vGRF was measured using F-Scan sensor. The experimental results showed that %MVIC was reduced against the external load applied, while GRF had a decrement rate, compared with the external load when the exoskeleton was worn, which verified the performance in accordance with the development objective of load carrying. A muscle strength augment effect from the developed wearable robot was verified.

A new design of a magnetorheological piston prototype intended for passive or active force control in robotic applications for human robot interaction is introduced. It is based in a novel toroidal array of valves, contained within the piston head, which are used to control the output force of the actuator in order to achieve a high degree of reliability, size efficiency, and safety, by exploiting the material properties of magnetorheological fluids and permalloy metals. This paper describes the main points in the development of the magnetorheological piston prototype, the mathematical modelling of the magnetic circuit, and the results of the experiments conducted using a universal testing machine to evaluate the passive performance of the prototype. Results show the feasibility and performance of the new toroidal magnetic circuit of the magnetorheological hydraulic piston prototype. Improvements in order to be able to test the active performance of the design together with a pump setup are proposed.

In this paper, the development and the experimental testing phases of an innovative assistive device for hand disabilities are presented. This robotic device is based on an parallel kinematic chain applied to a single phalanx architecture and it is designed to be extremely portable to easily assist people with physical disabilities in their everyday lives. Focusing on patients with hand opening disabilities, the authors have developed a model-based methodology which starting from the motion capture of the patient fingertip trajectories is able to define the mechanism that better fits with such trajectories. The authors have validated the proposed innovative mechanism by developing a portable Hand Exoskeleton System (HES) prototype and performing a suitable preliminary testing campaign. The testing phase of the real prototype on a group of patients is currently ongoing.

This paper presents the design, development and magnetic resonance imagining (MRI) compatibility evaluation of a small size, compact and adjustable different finger phalange lengths rehabilitation device. This device employs ultrasonic motor as its actuator and adopts a novel six-link mechanism to drive the finger. The final system enables to provide two joints (the MCP and the PIP) in each finger to do flexion and extension motion with one degree of freedom (DOF). The MRI compatibility of the robot was also evaluated. The results demonstrate that there is neither an effect from the MRI environment on the robot performance, nor significant degradation on MRI images by the introduction of the robot in the MRI scanner. Finally, an fMRI study with subject was carried out, the result shows a stable brain activation was observed when the middle finger of the subject was driven to implement passive rehabilitation motion inside the MRI scanner.

Incorporating the body dynamics of compliant robots into their controller architectures can drastically reduce the complexity of locomotion control. An extreme version of this embodied control principle was demonstrated in highly compliant tensegrity robots, for which stable gait generation was achieved by using only optimized linear feedback from the robot's sensors to its actuators. The morphology of quadrupedal robots has previously been used for sensing and for control of a compliant spine, but never for gait generation. In this paper, we successfully apply embodied control to the compliant, quadrupedal Oncilla robot. As initial experiments indicated that mere linear feedback does not suffice, we explore the minimal requirements for robust gait generation in terms of memory and nonlinear complexity. Our results show that a memoryless feedback controller can generate a stable trot by learning the desired nonlinear relation between the input and the output signals. We believe this method can provide a very useful tool for transferring knowledge from open loop to closed loop control on compliant robots.