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Hybrid Controller for Robot Manipulators in Task-Space with Visual-Inertial Feedback

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arXiv 2023年

作者： Hashemi, Seyed Hamed Mattila, Jouni The Unit of Automation Technology and Mechanical Engineering Faculty of Engineering and Natural Sciences Tampere University Tampere Finland

This paper presents a visual-inertial-based control strategy to address the task space control problem of robot manipulators. To this end, an observer-based hybrid controller is employed to control end-effector motion. In addition, a hybrid observer is introduced for a visual-inertial navigation system to close the control loop directly at the Cartesian space by estimating the end-effector pose. Accordingly, the robot's tip is equipped with an inertial measurement unit (IMU) and a stereo camera to provide task-space feedback information for the proposed observer. It is demonstrated through the Lyapunov stability theorem that the resulting closed-loop system under the proposed observer-based controller is globally asymptotically stable. Besides this notable merit (global asymptotic stability), the proposed control method eliminates the need to compute inverse kinematics and increases trajectory tracking accuracy in task-space. The effectiveness and accuracy of the proposed control scheme are evaluated through computer simulations, where the proposed control structure is applied to a 6 degrees-of-freedom long-reach hydraulic robot manipulator. Copyright © 2023, The Authors. All rights reserved.

关键词： Industrial robots

Squeeze-in Functionality for a Soft Parallel Robot Gripper

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Squeeze-in Functionality for a Soft Parallel Robot Gripper

IEEE International Conference on Soft Robotics (RoboSoft)

作者： Metodi Netzev Alexandre Angleraud Roel Pieters Cognitive Robotics group Tampere University Unit of Automation Technology and Mechanical Engineering Tampere Finland

Grasping parts of inconsistent shapes, sizes and weights securely requires accurate part models and custom gripper fingers. Compliant grippers are a potential solution; however, each design approach requires the solution of unique problems. In this case, the durability and reliability of half lips (at least 1400 cycles) to perform consistently as springs of a specified stiffness (0.5N/mm) and displacement (5mm). Moreover, the challenge of low and small (3mm, 0.01kg bolt or Allen key) objects is addressed through vertical squeeze-in, implemented using an incline, lip and flex limiter as part of a 3D printed TPC spring. The squeeze-in phenomena are verified on large objects through a 30mm, 1.66kg common rail. Experimental results demonstrate the reliability when given a human-specified location for gripping, without the need for jigs or fixtures. Finally, the tested design is assessed for potential fulfillment of 7 of the united Nations sustainable development goals.

关键词： Rails Parallel robots Flexible printed circuits Service robots Lips Grasping Reliability

Instructing Hierarchical Tasks to Robots by Verbal Commands

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arXiv 2023年

作者： Telkes, Péter Angleraud, Alexandre Pieters, Roel Cognitive Robotics group Unit of Automation Technology and Mechanical Engineering Tampere University Tampere33720 Finland

Natural language is an effective tool for communication, as information can be expressed in different ways and at different levels of complexity. Verbal commands, utilized for instructing robot tasks, can therefor replace traditional robot programming techniques, and provide a more expressive means to assign actions and enable collaboration. However, the challenge of utilizing speech for robot programming is how actions and targets can be grounded to physical entities in the world. In addition, to be time-efficient, a balance needs to be found between fine- and course-grained commands and natural language phrases. In this work we provide a framework for instructing tasks to robots by verbal commands. The framework includes functionalities for single commands to actions and targets, as well as longer-term sequences of actions, thereby providing a hierarchical structure to the robot tasks. Experimental evaluation demonstrates the functionalities of the framework by human collaboration with a robot in different tasks, with different levels of complexity. The tools are provided open-source at https://***/voice-jogger/ © 2023, CC BY.

关键词： Robot programming

Automatic Robot Path Planning for Visual Inspection from Object Shape

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arXiv 2023年

作者： Tasneem, Osama Pieters, Roel Cognitive Robotics group Unit of Automation Technology and Mechanical Engineering Tampere University Tampere33720 Finland

Visual inspection is a crucial yet time-consuming task across various industries. Numerous established methods employ machine learning in inspection tasks, necessitating specific training data that includes predefined inspection poses and training images essential for the training of models. The acquisition of such data and their integration into an inspection framework is challenging due to the variety in objects and scenes involved and due to additional bottlenecks caused by the manual collection of training data by humans, thereby hindering the automation of visual inspection across diverse domains. This work proposes a solution for automatic path planning using a single depth camera mounted on a robot manipulator. Point clouds obtained from the depth images are processed and filtered to extract object profiles and transformed to inspection target paths for the robot end-effector. The approach relies on the geometry of the object and generates an inspection path that follows the shape normal to the surface. Depending on the object size and shape, inspection paths can be defined as single or multi-path plans. Results are demonstrated in both simulated and real-world environments, yielding promising inspection paths for objects with varying sizes and shapes. © 2023, CC BY.

关键词： Inspection

Reinforcement Learning for Reliable Power Allocation and Load Mitigation in Wind Farm

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Reinforcement Learning for Reliable Power Allocation and Loa...

International Conference on Renewable Energy and Power engineering (REPE)

作者： Yazhou Wu Hamed Badihi Liyan Wen Xueqian Fu Yali Xue College of Automation Engineering Nanjing University of Aeronautics and Astronautics Nanjing China Automation Technology and Mechanical Engineering Unit Tampere University Tampere Finland College of Information and Electrical Engineering China Agricultural University Beijing China

ISBN: (数字)9798350375558

ISBN: (纸本)9798350375565

Wind energy is increasingly recognized as a key element in advancing a sustainable energy infrastructure and achieving carbon neutrality. However, the integration of wind power into the electrical grid presents significant challenges, particularly in maintaining grid frequency stability due to the variable and unpredictable nature of wind. This often necessitates precise control of power generation, which, in turn, imposes additional fatigue loads on wind turbines. Mitigating these loads is essential for lowering maintenance costs and enhancing turbine longevity. Recent advances in data-driven approaches have shown promise in optimizing power generation and grid frequency control. Notably, reinforcement learning has a natural advantage in solving complex optimization and control problems. This paper presents a novel application of RL for active power control within wind farms, aiming to devise effective power allocation strategies that minimize fatigue loads. Based on shaft torque and tower bending moment information, which are related to wind turbine fatigue, an advanced RL-based controller is designed and trained through iterative interaction with the operational environment. Furthermore, the control effectiveness is evaluated across various operational conditions. The findings confirm that the controller performs satisfactorily in mitigating fatigue loads, highlighting its viability for real-world implementation.

关键词： Shafts Torque Loading Poles and towers Reinforcement learning Wind farms Bending Fatigue Wind turbines Resource management

Data-driven Diffusion Models for Enhancing Safety in Autonomous Vehicle Traffic Simulations

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arXiv 2024年

作者： Lu, Jinxiong Azam, Shoaib Alcan, Gokhan Kyrki, Ville The Department of Electrical Engineering and Automation School of Electrical Engineering Aalto University Espoo02150 Finland Finnish Center for Artificial Intelligence Finland Automation Technology and Mechanical Engineering Unit The Faculty of Engineering and Natural Sciences Tampere University Finland

Safety-critical traffic scenarios are integral to the development and validation of autonomous driving systems. These scenarios provide crucial insights into vehicle responses under high-risk conditions rarely encountered in real-world settings. Recent advancements in critical scenario generation have demonstrated the superiority of diffusion-based approaches over traditional generative models in terms of effectiveness and realism. However, current diffusion-based methods fail to adequately address the complexity of driver behavior and traffic density information, both of which significantly influence driver decision-making processes. In this work, we present a novel approach to overcome these limitations by introducing adversarial guidance functions for diffusion models that incorporate behavior complexity and traffic density, thereby enhancing the generation of more effective and realistic safety-critical traffic scenarios. The proposed method is evaluated on two evaluation metrics: effectiveness and *** proposed method is evaluated on two evaluation metrics: effectiveness and realism, demonstrating better efficacy as compared to other state-of-the-art methods. © 2024, CC BY.

关键词： Autonomous vehicles

Distributed Impedance Control of Coordinated Dissimilar Upper-Limb Exoskeleton Arms

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TechRxiv

TechRxiv 2022年

作者： Tahamipour, Mohammad S.Z. Mattila, Jouni Automation Technology and Mechanical Engineering Unit Tampere University Tampere33720 Finland

Upper-limb exoskeleton (ULE) arms have the potential to assist humans in accomplishing tasks by distributing a heavy load. ULE arms are designed to be comfortable and lightweight wearable robotic devices, a design that has resulted in the complexity of their structures, actuators, and power transmissions. Additionally, different ULE vendor structures and biomechanical variations between humans have resulted in dissimilar coordinated ULE arm systems. These complex multiple ULE arm systems can be handled through adaptive virtual decomposition control (VDC) if unknown dynamic models are not considered. Accordingly, this paper proposes a new distributed framework for the adaptive impedance-based VDC method to address the abovementioned challenges and thereby enhance the performance and robustness of the ULE arm systems. To that end, the proposed control method has a prediction capability and an ancillary control law for coordinated dissimilar ULE arms holding a common object. The system stability is analyzed using the input-to-state stability approach. The performance of the proposed controller is evaluated both in simulation with six coordinated ULE arms and in an experiment with two commercial coordinated ULE arms each with seven degrees of freedom. Four scenarios are performed with different internal arm forces with and without an obstacle. The simulation and experiment results are compared with a state-of-the-art adaptive VDC method and show the superiority of the proposed control method. © 2022, CC BY.

关键词： Degrees of freedom (mechanics)

Dynamic Accuracy Optimization for NC controlled Industrial Robots

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Dynamic Accuracy Optimization for NC controlled Industrial R...

International Conference on Emerging Technologies and Factory automation (ETFA)

作者： Asier Mandiola Mikel Armendia Diego Gonzalez Jon Eguskiza Automation and Control Unit TEKNIKER Basque Research and Technology Alliance (BRTA) Eibar Spain Mechanical Engineering Unit TEKNIKER Basque Research and Technology Alliance (BRTA) Eibar Spain

In the last years the usage of industrial robotic manipulators is being extended to new applications, like laser or machining-based manufacturing. These applications require new user interface functionalities coming from common NC control systems, as well as increased demands in path tracking, dynamics, and accuracy. In this paper, a Dynamic Accuracy Optimization strategy is applied on a NC controlled industrial manipulator to minimize robot Tool Center Point errors during path execution. A state-of-the-art laser tracker system is used for online characterization of the TCP position which is fed to the compensation algorithm integrated in the NC controller. A drastic reduction of static and dynamic errors has been observed in both linear and orientation degrees of freedom, impacting also in the resulting path errors.

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Analytic Solutions for Wheeled Mobile Manipulator Supporting Forces

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arXiv 2022年

作者： Petrović, Goran R. Mattila, Jouni Faculty of Engineering and Natural Sciences Unit of Automation Technology and Mechanical Engineering Tampere University Tampere Finland

When a mobile manipulator’s wheel loses contact with the ground, tipping-over may occur, causing material damage, and in the worst case, it can put human lives in danger. The tip-over stability of wheeled mobile manipulators must not be overlooked at any stage of a mobile manipulator’s life, starting from the design phase, continuing through the commissioning period and extending to the operational phase. Many tip-over stability criteria formulated throughout the years do not explicitly consider the normal wheel loads, with most of them relying on prescribed stability margins in terms of overturning moments. In these formulations, it is commonly argued that overturning will occur about one of the axes connecting adjacent manipulator’s contact points with the ground. This claim may not always be valid and is certainly restrictive. Explicit expressions for the manipulator supporting forces provide the best insight into relevant affecting terms which contribute to the tip-over (in)stability. They also remove the necessity for thinking about which axis the manipulator could tip over and simultaneously enable the formulation of more intuitive stability margins and on-line tip-over prevention techniques. The present study presents a general dynamics modelling approach in the Newton–Euler framework using 6D vectors and gives normal wheel load equations in a typical 4-wheeled mobile manipulator negotiating a slope. The given expressions are expected to become standard in wheeled mobile manipulators and to provide a basis for effective tip-over stability criteria and tip-over avoidance techniques. Based on the presented results, specific improvements of the state-of-the-art criteria are discussed. Copyright © 2022, The Authors. All rights reserved.

关键词： Manipulators