A novel approach to micro-telemanipulation with soft slave robots: integrated design of a non-overshooting series elastic actuator

Micro mechanical devices are becoming ubiquitous as they find increas- ing uses in applications such as micro-fabrication, micro-surgery and micro- probing. Use of micro-electromechanical systems not only offer compactness and precision, but also increases the efficiency of processes. Whenever me- chanical devices are used to interact with the environment, accurate control of the forces arising at the interaction surfaces arise as an important chal- lenge. In this work, we propose using a series elastic actuation (SEA) for micro- manipulation. Since an SEA is an integrated mechatronic device, the me- chanical design and controller synthesis are handled in parallel to achieve the best overall performance. The mechanical design of the μSEA is handled in two steps: type selection and dimensional synthesis. In the type selection step, a compliant, half pantograph mechanism is chosen as the underlying kinematic structure of the coupling element. For optimal dimensioning, the bandwidth of the system, the disturbance response and the force resolution are considered to achieve good control performance with high reliability. These objectives are achieved by optimizing the manipulability and the stiffness of the mechanism along with a robustness constraint. In parallel with the mechanical design, a force controller is synthesized. The controller has a cascaded structure: an inner loop for position control and an outer loop for force control. Since excess force application can be detrimental during manipulation of fragile objects; the position controller of the inner loop is designed to be a non-overshooting controller which guar- antees the force response of the system always stay lower than the reference value. This self-standing μSEA system is embedded into a 3-channel scaled tele- operation architecture so that an operator can perform micro-telemanipulation. Constant scaling between the master and the slave is implemented and the teleoperator controllers preserve the non-overshooting nature of the μSEA. Finally, the designed μSEA based micro-telemanipulation system is im- plemented and characterized

Task Learning for Intention Detection using Deep Neural Networks and Robotic Arm Data in Glovebox

Tele-manipulation systems are becoming more reliant on complex local (master) devices with sophisticated control methods; hence, the cognitive load on the operator during labour intensive tasks is increasing. The operator intention detection based on task learning can lead to better robot task performance with less human effort in teleoperation for a glovebox environment (see Fig. 1). Deep Convolutional Neural Networks are proposed to learn and predict the operator intention using robotic arm and its controller spatiotemporal data. Our preliminary experimental study on glovebox tasks for nuclear applications, particularly radiation survey and object grasping, provided promising results and encouraged us for a deeper research.UK Atomic Energy Authority, Remote Applications in Challenging Environments, Robotics and AI in Nuclear (RAIN Hub

A variable-fractional order admittance controller for pHRI

In today’s automation driven manufacturing environments, emerging technologies like cobots (collaborative robots) and augmented reality interfaces can help integrating humans into the production workflow to benefit from their adaptability and cognitive skills. In such settings, humans are expected to work with robots side by side and physically interact with them. However, the trade-off between stability and transparency is a core challenge in the presence of physical human robot interaction (pHRI). While stability is of utmost importance for safety, transparency is required for fully exploiting the precision and ability of robots in handling labor intensive tasks. In this work, we propose a new variable admittance controller based on fractional order control to handle this trade-off more effectively. We compared the performance of fractional order variable admittance controller with a classical admittance controller with fixed parameters as a baseline and an integer order variable admittance controller during a realistic drilling task. Our comparisons indicate that the proposed controller led to a more transparent interaction compared to the other controllers without sacrificing the stability. We also demonstrate a use case for an augmented reality (AR) headset which can augment human sensory capabilities for reaching a certain drilling depth otherwise not possible without changing the role of the robot as the decision maker

The potential for haptic-enabled interaction to support collaborative learning in school biology

This paper discusses the rationales and design considerations for developing the use of haptics (virtual touch) for learning aspects of cell biology in secondary schools. The paper considers issues in understanding concepts in cell biology and how a 3-D environment enabled by haptics could support learning of difficult concepts. In this endeavour, a number of educational and design challenges need to be addressed. First we need to identify the level of detail and realism that will support learning and visualisation rather than confuse through its overcomplexity or create misconceptions through oversimplification. Secondly we need to integrate the use of the 3-D environment into classroom teaching by identifying relevant curriculum and pedagogical challenges and solutions. Significant design challenges include navigating the content and scale changes involved in moving between the visible, microscopic and nanoscale in an intuitive and realistic way and enabling collaborative learning

Haptic-enabled collaborative learning in virtual reality for schools

This paper reports on a study which designed and developed a multi-fingered haptic interface in conjunction with a three-dimensional (3D) virtual model of a section of the cell membrane in order to enable students to work collaboratively to learn cell biology. Furthermore, the study investigated whether the addition of haptic feedback to the 3D virtual reality (VR) simulation affected learning of key concepts in nanoscale cell biology for students aged 12 to 13. The haptic interface was designed so that the haptic feedback could be turned on or switched off. Students (N = 64), in two secondary schools, worked in pairs, on activities designed to support learning of specific difficult concepts. Findings from observation of the activities and interviews revealed that students believed that being immersed in the 3D VR environment and being able to feel structures and movements within the model and work collaboratively assisted their learning. More specifically, the pilot/co-pilot model that we developed was successful for enabling collaborative learning and reducing the isolating effects of immersion with a 3D headset. Results of pre and post-tests of conceptual knowledge showed significant knowledge gains but addition of haptic feedback did not affect the knowledge gains significantly. The study enabled identification of important issues to consider when designing and using haptic-enabled 3D VR environments for collaborative learning

Stability of haptic systems with fractional order controllers

Fractional order calculus is a generalization of the familiar integer order calculus in that, it allows for differentiation/integration with orders of any real number. The use of fractional order calculus in systems and control applications provides the user an extra design variable, the order of differointegration, which can be tuned to improve the desired behavior of the overall system. We propose utilization of fractional order models/controllers in haptic systems and study the effect of fractional differentiation order on the stability robustness of the overall sampled-data system. Our results demonstrate that fractional calculus generalization has a significant impact on both the shape and area of stability region of a haptic system and inclusion of fractional order impedances may improve the stability robustness of haptic rendering. Our results also include experimental verification of the stability regions predicted by the theoretical analysis

Robust optimal design of a micro gripper

This paper presents the robust optimal design of a compliant, parallel mechanism based micro gripper. Multiple design objectives are considered for the gripping task and a compliant, under-actuated micro mechanism, namely a half-pantograph, is chosen as a feasible kinematic structure of the gripper. An optimization problem to study the trade-offs between multiple design criteria is formulated and dimensional synthesis of the mechanism is performed to achieve the proper directional task space stiffness of the device, while simultaneously maximizing its manipulability, using a Pareto-front based framework. The design framework is extended by adding robustness considerations of the mechanism into the design phase. In particular, the performance of the system under variation of the design variables is analyzed using the sensitivity region concept and a family of robust Pareto-front curves are calculated. A final design is chosen from a robust Pareto-front curve based on performance threshold and a secondary design criteria that considers the torsional and unidirectional stiffness of the mechanism at the task space

Optimal design of a micro series elastic actuator

We propose using series elastic actuation (SEA) in micro mechanical devices to achieve precise control of the interaction forces. Using SEA for force control removes the need for high-precision force sensors/actuators and allows for accurate force control through simple position control of the deflection of a compliant coupling element. Since the performance of a SEA is highly dependent on the design of this compliant coupling element, we employ a design optimization framework to design this element. In particular, we propose a compliant, under-actuated half-pantograph mechanism as a feasible kinematic structure for this coupling element. Then, we consider multiple design objectives to optimize the performance of this compliant mechanism through dimensional synthesis, formulating an optimization problem to study the trade-offs between these design criteria. We optimize the directional manipulability of the mechanism, simultaneously with its task space stiffness, using a Pareto-front based framework. We select an optimal design by studying solutions on the Pareto-front curve and considering the linearity of the stiffness along the actuation direction as a secondary design criteria. The optimized mechanism possesses high manipulability and low stiffness along the movement direction of the actuator; hence, achieves a large stroke with high force resolution. At the same time, the mechanism has low manipulability and high stiffness along the direction perpendicular to the actuator motion, ensuring good disturbance rejection characteristics. We model the behavior of this compliant mechanism and utilize this model to synthesize a controller for SEA to study its dynamic response. Simulated closed loop performance of the SEA with optimized coupling element indicates that force references can be tracked without significant overshoot and with low tracking error (about 1.1 percent) even for periodic reference signals

Series elastic actuation for force controlled micro-manipulation

We propose using series elastic actuation (SEA) in micro mechanical devices to achieve precise control of the interaction forces. Using mSEA for force control removes the need for high-precision force sensors/actuators and allows for accurate force control through simple position control of the deflection of a compliant coupling element. In this work, we employ a design optimization framework to design this element. The proposed design framework ensures robustness of the design while simultaneously optimizing multiple objective functions. The robust design optimization method relies on the Sensitivity Region concept which minimizes the change of the objective function with respect to the small changes in the design variables. Once the optimal design is obtained, a non-overshooting controller is implemented for the mSEA to achieve accurate force tracking without ever exceeding the reference force input