Gonzalo Aguirre Dominguez

A Concept for a robot arm with adjustable series clutch actuators and passive gravity compensation for enhanced safety

Passive compliance is useful for robotic arms to ensure their safety. Often springs are used, but they are problematic because they reduce the achievable accelerations and can lead to underdamped oscillations. Torque limiters enhance the safety, but usually the torque limit cannot be adjusted to a desired torque. Electronically adjustable torque limiters, also known as series clutch actuators, have several benefits, especially for robotic arms, but they also have severe limitations. This paper suggests incorporating series clutch actuators into a gravity compensated arm. Consequently, gravity should not limit the isotropically achievable force anymore and in the case of power outage the arm keeps its position. The benefits and limitations of a series clutch actuator in a gravity compensated arm are discussed, and a prototype of such an arm is presented. Commercially available magnetic friction clutches are used. Preliminary experiments demonstrate that the safety can be increased.

Development of a backdrivable magnetorheological hydraulic piston for passive and active linear actuation

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.

Development of a tele-operation simulator based on virtual reality environment for advanced unmanned construction

This paper describes a tele-operation simulator using a virtual reality (VR) environment for advanced unmanned construction. VR simulators, which can measure arbitrary data, reproduce the same situations, and change the machine and environmental configurations more easily, compared with actual environments, are effective to create tele-operation technologies and quantitatively evaluate them as well as to improve operational skills in complex disaster response works. In this basic study, a VR simulator including a VR environment, operation-input, and video-output components was developed. (i) The VR environment is built using a basic graphic library and dynamics engine. (ii) The operation-input component consists of control levers for a demolition machine with a grapple and environmental cameras with yaw, pitch, and zoom functions. (iii) The video-output component consists of a two-dimensional monitor for displaying an in-vehicle camera view, environmental camera views, and machine status. The results of experiments conducted to transport debris using the VR simulator indicated that the operators adequately completed the debris transport in the VR environment while watching the monitor views from the in-vehicle and environmental cameras.

Modelling and simulation of a new magnetorheological linear device

Interaction between humans and robots is expected to increase in the coming years. In order to ensure safety for the robot, its environment, and the people around it, it is necessary to have robust compliance actuation. Mechanically compliant devices such as magnetorheological actuators can ensure a high degree of safety through their intrinsic properties. This paper presents the modelling of a new kind of magnetorheological piston intended for linear actuation. An analysis using the reluctance method and an approximation of the Buckingham Reiner equation are used to develop the electromagnetic and hydraulic equations respectively, and key parameters of the system are presented. A simulation is done to evaluate the theoretical performance of the new piston design, its results are compared and validated by the experimental data obtained from a prototype. The simulation results show the capacity of the device for compliant actuation.

Proposal and Preliminary Feasibility Study of a Novel Toroidal Magnetorheological Piston

A new magnetorheological piston head design inspired by toroidal electromagnets was proposed in previous work as an alternative to conventional annular dampers. A prototype with a circular valve array integrated inside the piston head was built and tested to measure its passive performance. The mechanical, electromagnetic, and hydraulic models used in the new design were explained, and the relevant parameters of the actuator were analyzed to construct a mathematical model to estimate its performance. These works showed the feasibility of the concept and its potential as an alternative to current damper technology, but lacked a baseline for comparison. This paper reviews and widens this groundwork. It adds a magnetic finite element method study to address the previously found leakage, and a new set of experiments, including a force controller, to compare its performance against a conventional annular piston head. The new findings show how the current force limitations can be overcome by striking a balance between the coil space and the size of electromagnet cores to achieve the performance of current dampers. They also highlight its potential in force control applications to provide a wider range of customization options, such as number and size of holes, electromagnets, and coils, and a better use of the active area of the gap.

An iterative design methodology for the performance optimisation of magnetorheological piston head configurations

This work focuses on the analysis of the performance parameters of a new magneto-rheological device. Previously, a mathematical model of the actuator head was introduced; however, the complex relations between its parameters made its optimisation challenging, causing the device not to reach its full potential. In this work, the previous model is updated to fit a revised version of the toroidal design, as well as an annular design for comparison. The relations between different parameters are studied to find their trade-offs, and understand how they affect the performance of the actuators. Finally, an optimisation based on an iterative search for valid permutations of parameters, is used to find optimal combinations. Two prototypes are built and tested to validate the results of the optimisation. The study revealed the critical parameters of each design, which mostly depend on the relations between the magnetic flux density, and the active area exposed to the MRF; and successfully optimised the performance of the devices. However, work needs to be done to create a more complete tool with concrete guidelines for specific applications.

Design optimisation and performance evaluation of a toroidal magnetorheological hydraulic piston head

The advantages of mechanical compliance have driven the development of devices using new smart materials. A new kind of magnetorheological piston based on a toroidal array of magnetorheological valves, has been previously tested to prove its feasibility. However, being an initial prototype its potential was still limited by its complex design, and low output force. This study presents the revisions done to the design with several improvements targeting key performance parameters. An improved annular piston design is also introduced as comparison with conventional devices. The toroidal and annular piston head prototypes are built and tested, and their force performance compared with the previous iteration. The experimental results show an overall performance improvement of the toroidal assembly. However, the force model used in the study still fails to accurately predict the magnetic flux at the gaps of the piston head. This deviation is later verify and corrected using a FEM analysis. The force performance of the new toroidal assembly is on par with the commonplace annular design. It also displays a more linear behaviour, at the expense of lower energy efficiency. Finally, it also shows potential for a greater degree of customisation to meet different system requirements.

Novel Social Innovation Concept Based on the Viewpoint of the Infrastructure User

Recently, due to the deceleration of the markets in developed economies, the growing demand for infrastructure development in emerging countries has become more important in the global economy. Conventionally, developed countries have improved their infrastructure from governments and suppliers viewpoints. However, this approach has not always been the best when working in emerging countries. In this study, we propose an innovative approach inspired by the concept of social innovation, centered around the social viewpoint. It consists of a system for the successful implementation and sustainable development of new infrastructure projects in emerging countries. We focus on an ongoing railway project in Vietnam by looking at the applicability of this concept there. Finally, the concept is evaluated through rounds of discussion with experts from the government, academia and industry. It was concluded that the project is perceived to have great potential for the region, and it is regarded with high esteem by all stakeholders.

A Haptic interface with adjustable stiffness using MR fluid sophon somlor

This paper describes a combined tactile sensor and haptic interface that can change its stiffness using magnetorheological fluids (MR fluid). The tactile sensor consists of 6 distributed capacitive sensors that can sense the location and the amount of applied force. Above the sensors is a chamber filled with MR fluid. By changing the magnetic field, the hardness of the MR fluid, and thereby of the haptic interface, can be changed. Fast changes of the magnetization direction lead to a sensation of vibration. The resulting device can be used for novel haptic input devices or for robotic grippers. A prototype device has been constructed, and the effects of the varying magnetic field and the resulting varying stiffness of the MR fluid on the distributed force sensing with the capacitive sensors has been evaluated. We discovered that the measured forces vary very little with changes in the strength of the magnetic field.