Shared Autonomy via Hindsight Optimization

In shared autonomy, user input and robot autonomy are combined to control a robot to achieve a goal. Often, the robot does not know a priori which goal the user wants to achieve, and must both predict the user's intended goal, and assist in achieving that goal. We formulate the problem of shared autonomy as a Partially Observable Markov Decision Process with uncertainty over the user's goal. We utilize maximum entropy inverse optimal control to estimate a distribution over the user's goal based on the history of inputs. Ideally, the robot assists the user by solving for an action which minimizes the expected cost-to-go for the (unknown) goal. As solving the POMDP to select the optimal action is intractable, we use hindsight optimization to approximate the solution. In a user study, we compare our method to a standard predict-then-blend approach. We find that our method enables users to accomplish tasks more quickly while utilizing less input. However, when asked to rate each system, users were mixed in their assessment, citing a tradeoff between maintaining control authority and accomplishing tasks quickly

Determination of the hydrodynamic performance of marine propellers using fibre Bragg gratings

Downloading of the abstract is permitted for personal use only. A critical aspect in the design of marine propellers is their hydrodynamic performance which, when evaluated experimentally, requires a number of parameters to be monitored at the same time, i.e.The thrust and torque a propeller generates as well as the propeller shaft and vessel speed. In this investigation, three of those parameters are measured using Fibre Bragg Grating-based sensors, thus allowing for computationally derived performance values to be verified. For that purpose, open water tests were carried out where an instrumented propeller shaft was installed into a research vessel and measurements taken, evaluated and the results compared favorably with advanced computer-based simulations

Underwater free-vibration analysis of full-scale marine propeller using a Fibre Bragg Grating-based sensor system

A detailed experimentally-based study has been carried out on instrumented, full-scale marine propeller blades in order to investigate their vibration behaviour, both in air and underwater. To obtain data with minimum perturbation to the characteristics of the blades, a Fibre Bragg Grating-based sensor network system was designed and implemented, for the first time. The individual vibration frequencies at each measurement point and thus the broader vibration patterns seen for each of the blades were obtained, with excitation both in air and in water and the results are compared favourably with those obtained from Finite Element (FE) analysis. The vibration patterns obtained show that the same modes of vibration occur in air and in water, although in some natural frequencies the mode order is seen to change from one blade to another on the same propeller. The extensive performance survey carried out and experimental data obtained have also shown that while the effect of the added mass of water on the natural frequencies of the blades in the fundamental modes is considerable, this effect diminishes as the natural frequencies of the blades increase. The results obtained from the optical fibre sensor network were compared to those from previous work in this area using different and less satisfactory techniques and it was confirmed that the ratio of the natural frequencies in water to those in air increases in a linear manner as the frequencies were increasing. Additionally, the natural frequencies of a blade were measured under different depths of propeller immersion

Fiber bragg grating-based system for 2-D analysis of vibrational modes of a steel propeller blade

This paper reports results obtained using fiber Bragg grating (FBG)-based sensors to investigate the displacement mode shapes of a cantilevered steel propeller blade, using FBG arrays for vibration monitoring for the first time. The experimental data obtained are cross compared with those from a finite element analysis of the same blade, undertaken using proprietary software. In the experimental configuration used, a network of gratings, forming a series of sensor arrays, was mounted on the blade under study to monitor its bending modes, while a further set was mounted perpendicular to this array to monitor torsional modes. To obtain the shape of the strain modes generated in the blade at specific frequencies, the dynamic response of the FBG arrays, as a function of time, was captured and then processed using Fourier transform algorithms to show the natural frequencies of the blade. As a result, the displacement modes shapes for the bending, torsional, and coupled modes of the first nine natural frequencies of the plate were obtained. The experimental data show very good agreement with theoretical analysis. This paper demonstrates the potential of using the lightweight, minimally invasive sensing technique described for the analysis of propeller blades and, thus, illustrating an effective method to overcome the deleterious effects of propellers seen in some commercial propeller designs

Radiographic comparison of five different techniques for injection into the distal sesamoid bursa in cattle

Summary Numerous techniques for injection into the distal sesamoid bursa (navicular bursa) have been described, especially in equine, but there are few specific descriptions regarding this practice being done in cattle. Five different techniques were compared for injection into the distal sesamoid bursa in cattle including distal plantar approach parallel with the coronary band, proximal plantar approach, distal plantar approach parallel with the sole, abaxial approach, and distal interphalangeal joint injection. The results revealed that the numbers of needle insertion until proper placement is significantly less in the DIPJ and the DPPS techniques compared to the others (P<0.05). Also, based on the times of contrast agent injection after the correct successful needle insertion, there were significant differences between DIPJ with DPPCB, PP30 and the Ab45 techniques (P<0.05). According to the absence of direct communication between the distal sesamoid bursa and distal interphalangeal joint, the placement of the needle through distal plantar approach parallel with the sole was suggested

Optical fibre sensing: A solution for industry

Optical fibres have been explored widely for their sensing capability to meet increasing industrial needs, building on their success in telecommunications. This paper provides a review of research activities at City University of London in response to industrial challenges through the development of a range of fibre Bragg grating (FBG)-based sensors for transportation structural monitoring. For marine propellers, arrays of FBGs mapped onto the surface of propeller blades allow for capturing vibrational modes, with reference to simulation data. The research funded by EU Cleansky programme enables the development of self-sensing electric motor drives to support 'More Electric Aircraft' concept. The partnership with Faiveley Brecknell Willis in the UK enables the integration of FBG sensors into the railway current-collecting pantographs for real-time condition monitoring when they are operating under 25kV conditions

Mixed-Initiative Human-Automated Agents Teaming: Towards a Flexible Cooperation Framework

The recent progress in robotics and artificial intelligence raises the question of the efficient artificial agents interaction with humans. For instance, artificial intelligence has achieved technical advances in perception and decision making in several domains ranging from games to a variety of operational situations, (e.g. face recognition [51] and firefighting missions [23]). Such advanced automated systems still depend on human operators as far as complex tactical, legal or ethical decisions are concerned. Usually the human is considered as an ideal agent, that is able to take control in case of automated (artificial) agent's limit range of action or even failure (e.g embedded sensor failures or low confidence in identification tasks). However, this approach needs to be revised as revealed by several critical industrial events (e.g. aviation and nuclear power-plant) that were due to conflicts between humans and complex automated system [13]. In this context, this paper reviews some of our previous works related to human-automated agents interaction driving systems. More specifically, a mixed-initiative cooperation framework that considers agents' non-deterministic actions effects and inaccuracies about the human operator state estimation. This framework has demonstrated convincing results being a promising venue for enhancing human-automated agent(s) teaming