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1.	Almeida, Diogo, 1991-, et al. (författare) A Framework for Bimanual Folding Assembly Under Uncertainties 2017 Ingår i: Workshop – Towards robust grasping and manipulation skills for humanoids. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
2.	Almeida, Diogo, 1991-, et al. (författare) A Lyapunov-Based Approach to Exploit Asymmetries in Robotic Dual-Arm Task Resolution 2019 Ingår i: 58th IEEE Conference on Decision and Control (CDC). ; 2019-December, s. 4252-4258 Konferensbidrag (refereegranskat)abstract Dual-arm manipulation tasks can be prescribed to a robotic system in terms of desired absolute and relative motion of the robot’s end-effectors. These can represent, e.g., jointly carrying a rigid object or performing an assembly task. When both types of motion are to be executed concurrently, the symmetric distribution of the relative motion between arms prevents task conflicts. Conversely, an asymmetric solution to the relative motion task will result in conflicts with the absolute task. In this work, we address the problem of designing a control law for the absolute motion task together with updating the distribution of the relative task among arms. Through a set of numerical results, we contrast our approach with the classical symmetric distribution of the relative motion task to illustrate the advantages of our method.
3.	Almeida, Diogo, 1991-, et al. (författare) Asymmetric Dual-Arm Task Execution using an Extended Relative Jacobian 2019 Ingår i: The International Symposium on Robotics Research. Konferensbidrag (refereegranskat)abstract Coordinated dual-arm manipulation tasks can be broadly characterized as possessing absolute and relative motion components. Relative motion tasks, in particular, are inherently redundant in the way they can be distributed between end-effectors. In this work, we analyse cooperative manipulation in terms of the asymmetric resolution of relative motion tasks. We discuss how existing approaches enable the asymmetric execution of a relative motion task, and show how an asymmetric relative motion space can be defined. We leverage this result to propose an extended relative Jacobian to model the cooperative system, which allows a user to set a concrete degree of asymmetry in the task execution. This is achieved without the need for prescribing an absolute motion target. Instead, the absolute motion remains available as a functional redundancy to the system. We illustrate the properties of our proposed Jacobian through numerical simulations of a novel differential Inverse Kinematics algorithm.
4.	Almeida, Diogo, 1991-, et al. (författare) Asymmetric Dual-Arm Task Execution Using an Extended Relative Jacobian 2022 Ingår i: Springer Proceedings in Advanced Robotics. - Cham : Springer International Publishing. - 2511-1264 .- 2511-1256. ; 20 SPAR, s. 18-34, s. 18-34 Konferensbidrag (refereegranskat)abstract Coordinated dual-arm manipulation tasks can be broadly characterized as possessing absolute and relative motion components. Relative motion tasks, in particular, are inherently redundant in the way they can be distributed between end-effectors. In this work, we analyse cooperative manipulation in terms of the asymmetric resolution of relative motion tasks. We discuss how existing approaches enable the asymmetric execution of a relative motion task, and show how an asymmetric relative motion space can be defined. We leverage this result to propose an extended relative Jacobian to model the cooperative system, which allows a user to set a concrete degree of asymmetry in the task execution. This is achieved without the need for prescribing an absolute motion target. Instead, the absolute motion remains available as a functional redundancy to the system. We illustrate the properties of our proposed Jacobian through numerical simulations of a novel differential Inverse Kinematics algorithm.
5.	Almeida, Diogo, 1991-, et al. (författare) Bimanual folding assembly: Switched control and contact point estimation 2016 Ingår i: 16th IEEE-RAS International Conference on Humanoid Robots, Humanoids 2016; Hotel WestinCancun; Mexico; 15-17 November 2016. - Cancun : IEEE. - 2164-0580. - 9781509047185 ; , s. Art no 7803279, Pages 210-216 Konferensbidrag (refereegranskat)abstract Robotic assembly in unstructured environments is a challenging task, due to the added uncertainties. These can be mitigated through the employment of assembly systems, which offer a modular approach to the assembly problem via the conjunction of primitives. In this paper, we use a dual-arm manipulator in order to execute a folding assembly primitive. When executing a folding primitive, two parts are brought into rigid contact and posteriorly translated and rotated. A switched controller is employed in order to ensure that the relative motion of the parts follows the desired model, while regulating the contact forces. The control is complemented with an estimator based on a Kalman filter, which tracks the contact point between parts based on force and torque measurements. Experimental results are provided, and the effectiveness of the control and contact point estimation is shown.
6.	Almeida, Diogo, 1991-, et al. (författare) Cooperative Manipulation and Identification of a 2-DOF Articulated Object by a Dual-Arm Robot 2018 Ingår i: 2018 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA). - 1050-4729. - 9781538630815 ; , s. 5445-5451 Konferensbidrag (refereegranskat)abstract In this work, we address the dual-arm manipula-tion of a two degrees-of-freedom articulated object that consistsof two rigid links. This can include a linkage constrainedalong two motion directions, or two objects in contact, wherethe contact imposes motion constraints. We formulate theproblem as a cooperative task, which allows the employment ofcoordinated task space frameworks, thus enabling redundancyexploitation by adjusting how the task is shared by the robotarms. In addition, we propose a method that can estimate thejoint location and the direction of the degrees-of-freedom, basedon the contact forces and the motion constraints imposed bythe object. Experimental results demonstrate the performanceof the system in its ability to estimate the two degrees of freedomindependently or simultaneously.
7.	Almeida, Diogo, 1991-, et al. (författare) Dexterous manipulation by means of compliant grasps and external contacts 2017 Ingår i: 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2017. - : IEEE. - 9781538626818 ; , s. 1913-1920 Konferensbidrag (refereegranskat)abstract We propose a method that allows for dexterousmanipulation of an object by exploiting contact with an externalsurface. The technique requires a compliant grasp, enablingthe motion of the object in the robot hand while allowingfor significant contact forces to be present on the externalsurface. We show that under this type of grasp it is possibleto estimate and control the pose of the object with respect tothe surface, leveraging the trade-off between force control andmanipulative dexterity. The method is independent of the objectgeometry, relying only on the assumptions of type of grasp andthe existence of a contact with a known surface. Furthermore,by adapting the estimated grasp compliance, the method canhandle unmodelled effects. The approach is demonstrated andevaluated with experiments on object pose regulation andpivoting against a rigid surface, where a mechanical springprovides the required compliance.
8.	Almeida, Diogo, 1991-, et al. (författare) Dexterous manipulation with compliant grasps and external contacts 2017 Ingår i: IEEE International Conference on Intelligent Robots and Systems. - : IEEE. - 2153-0858 .- 2153-0866. ; 2017-September, s. 1913-1920 Konferensbidrag (refereegranskat)abstract We propose a method that allows for dexterous manipulation of an object by exploiting contact with an external surface. The technique requires a compliant grasp, enabling the motion of the object in the robot hand while allowing for significant contact forces to be present on the external surface. We show that under this type of grasp it is possible to estimate and control the pose of the object with respect to the surface, leveraging the trade-off between force control and manipulative dexterity. The method is independent of the object geometry, relying only on the assumptions of type of grasp and the existence of a contact with a known surface. Furthermore, by adapting the estimated grasp compliance, the method can handle unmodelled effects. The approach is demonstrated and evaluated with experiments on object pose regulation and pivoting against a rigid surface, where a mechanical spring provides the required compliance.
9.	Almeida, Diogo, 1991- (författare) Dual-Arm Robotic Manipulation under Uncertainties and Task-Based Redundancy 2019 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Robotic manipulators are mostly employed in industrial environments, where their tasks can be prescribed with little to no uncertainty. This is possible in scenarios where the deployment time of robot workcells is not prohibitive, such as in the automotive industry. In other contexts, however, the time cost of setting up a classical robotic automation workcell is often prohibitive. This is the case with cellphone manufacturing, for example, which is currently mostly executed by human workers. Robotic automation is nevertheless desirable in these human-centric environments, as a robot can automate the most tedious parts of an assembly. To deploy robots in these environments, however, requires an ability to deal with uncertainties and to robustly execute any given task. In this thesis, we discuss two topics related to autonomous robotic manipulation. First, we address parametric uncertainties in manipulation tasks, such as the location of contacts during the execution of an assembly. We propose and experimentally evaluate two methods that rely on force and torque measurements to produce estimates of task related uncertainties: a method for dexterous manipulation under uncertainties which relies on a compliant rotational degree of freedom at the robot's gripper grasp point and exploits contact with an external surface, and a cooperative manipulation system which is able to identify the kinematics of a two degrees of freedom mechanism. Then, we consider redundancies in dual-arm robotic manipulation. Dual-armed robots offer a large degree of redundancy which can be exploited to ensure a more robust task execution. When executing an assembly task, for instance, robots can freely change the location of the assembly in their workspace without affecting the task execution. We discuss methods that explore these types of redundancies in relative motion tasks in the form of asymmetries in their execution. Finally, we approach the converse problem by presenting a system which is able to balance measured forces and torques at its end-effectors by leveraging relative motion between them, while grasping a rigid tray. This is achieved through discrete sliding of the grasp points, which constitutes a novel application of bimanual dexterous manipulation.
10.	Almeida, Diogo, 1991-, et al. (författare) Folding Assembly by Means of Dual-Arm Robotic Manipulation 2016 Ingår i: 2016 IEEE International Conference on Robotics and Automation. - : IEEE conference proceedings. - 1050-4729. - 9781467380263 ; , s. 3987-3993 Konferensbidrag (refereegranskat)abstract In this paper, we consider folding assembly as an assembly primitive suitable for dual-arm robotic assembly, that can be integrated in a higher level assembly strategy. The system composed by two pieces in contact is modelled as an articulated object, connected by a prismatic-revolute joint. Different grasping scenarios were considered in order to model the system, and a simple controller based on feedback linearisation is proposed, using force torque measurements to compute the contact point kinematics. The folding assembly controller has been experimentally tested with two sample parts, in order to showcase folding assembly as a viable assembly primitive.
11.	Almeida, Diogo, 1991-, et al. (författare) Robotic Manipulation for Bi-Manual Folding Assembly 2015 Ingår i: Late Breaking Posters. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract In this poster the problem of bimanual robotic assembly is considered. In particular we introduce folding assembly which is an assembly task that requires significant rotational motion in order to mate two assembly pieces. We model the connection between the two parts as an ideal virtual prismatic and revolute joint while non-ideal effects on the part movements can be considered as special cases of the ideal virtual joint. The connection between the gripper and the assembly part is also studied by considering the case of rigid and non-rigid grasp. As a proof-of-concept, a stabilizing controller for the assembly task is derived following a bimanual master-slave approach under the assumption of rigid grasps. The controller is validated through simulation while an example object has been designed and printed for experimental validation of our assembly technique.
12.	Almeida, Diogo, 1991-, et al. (författare) Team KTH’s Picking Solution for the Amazon Picking Challenge 2016 2017 Ingår i: Warehouse Picking Automation Workshop 2017. Konferensbidrag (populärvet., debatt m.m.)abstract In this work we summarize the solution developed by Team KTH for the Amazon Picking Challenge 2016 in Leipzig, Germany. The competition simulated a warehouse automation scenario and it was divided in two tasks: a picking task where a robot picks items from a shelf and places them in a tote and a stowing task which is the inverse task where the robot picks items from a tote and places them in a shelf. We describe our approach to the problem starting from a high level overview of our system and later delving into details of our perception pipeline and our strategy for manipulation and grasping. The solution was implemented using a Baxter robot equipped with additional sensors.
13.	Almeida, Diogo, 1991-, et al. (författare) Team KTH’s Picking Solution for the Amazon Picking Challenge 2016 2020 Ingår i: Advances on Robotic Item Picking: Applications in Warehousing and E-Commerce Fulfillment. - Cham : Springer Nature. ; , s. 53-62 Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract In this chapter we summarize the solution developed by team KTH for the Amazon Picking Challenge 2016 in Leipzig, Germany. The competition, which simulated a warehouse automation scenario, was divided into two parts: a picking task, where the robot picks items from a shelf and places them into a tote, and a stowing task, where the robot picks items from a tote and places them in a shelf. We describe our approach to the problem starting with a high-level overview of the system, delving later into the details of our perception pipeline and strategy for manipulation and grasping. The hardware platform used in our solution consists of a Baxter robot equipped with multiple vision sensors.
14.	Arslan Waltersson, Gabriel, 1996, et al. (författare) Planar Friction Modelling with LuGre Dynamics and Limit Surfaces 2024 Ingår i: IEEE Transactions on Robotics. - 1552-3098 .- 1941-0468. ; 40, s. 3166-3180 Tidskriftsartikel (refereegranskat)abstract During planar motion, contact surfaces exhibit a coupling between tangential and rotational friction forces. This paper proposes planar friction models grounded in the LuGre model and limit surface theory. First, distributed planar extended state models are proposed and the Elasto-Plastic model is extended for multi-dimensional friction. Subsequently, we derive a reduced planar friction model coupled with a pre-calculated limit surface, that offers reduced computational cost. The limit surface approximation through an ellipsoid is discussed. The properties of the planar friction models are assessed in various simulations, demonstrating that the reduced planar friction model achieves comparable performance to the distributed model while exhibiting $\sim 80$ times lower computational cost.
15.	Arslan Waltersson, Gabriel, 1996, et al. (författare) Planning and Control for Cable-routing with Dual-arm Robot 2022 Ingår i: Proceedings - IEEE International Conference on Robotics and Automation. - 1050-4729. ; 2022-May, s. 1046-1052 Konferensbidrag (refereegranskat)abstract In this paper, we propose a new framework for solving cable-routing problems with a dual-arm robot, where the objective is to clip a Deformable Linear Object (DLO) into several arbitrarily placed fixtures. The core of the framework is a task-space planner, which builds a roadmap from predefined tasks and employs a replanning strategy based on a genetic algorithm, if problems occur. The manipulation tasks are executed with either individual or coordinated control of the arms. Moreover, hierarchical quadratic programming is used to solve the inverse differential kinematics together with extra feasibility objectives. A vision system first identifies the desired fixture route and structure preserved registration estimates the state of the DLO in real-time. The framework is tested on real-world experiments with a YuMi robot, demonstrating a 90% success rate for 3 fixture problems.
16.	Bekiroglu, Yasemin, et al. (författare) SARAFun, Smart Assembly Robot with Advanced FUNctionalities, H2020 2017 Ingår i: Impact. - : Science Impact, Ltd.. - 2398-7073. ; 2017:5, s. 67-69 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract While Industrial robots are very successful in many areas of industrial manufacturing, assembly automation still suffers from complex time consuming programming and the need of dedicated hardware. ABB has developed YuMi, a collaborative inherently safe assembly robot that is expected to reduce integration costs significantly by offering a standardized hardware setup and simple fitting of the robot into existing workplaces. Internal Pilot testing at ABB has however shown that when YuMi is programmed with traditional methods the programming time even for simple assembly tasks will remain very long. The SARAFun project has been formed to enable a non-expert user to integrate a new bi-manual assembly task on a YuMi robot in less than a day. This will be accomplished by augmenting the YuMi robot with cutting edge sensory and cognitive abilities as well as reasoning abilities required to plan and execute an assembly task. The overall conceptual approach is that the robot should be capable of learning and executing assembly tasks in a human like manner. Studies will be made to understand how human assembly workers learn and perform assembly tasks. The human performance will be modelled and transferred to the YuMi robot as assembly skills. The robot will learn assembly tasks, such as insertion or folding, by observing the task being performed by a human instructor. The robot will then analyze the task and generate an assembly program, including exception handling, and design 3D printable fingers tailored for gripping the parts at hand. Aided by the human instructor, the robot will finally learn to perform the actual assembly task, relying on sensory feedback from vision, force and tactile sensing as well as physical human robot interaction. During this phase the robot will gradually improve its understanding of the assembly at hand until it is capable of performing the assembly in a fast and robust manner.
17.	Bellone, Mauro, 1982, et al. (författare) Comparison of CNN and LSTM for modeling virtual sensors in an engine 2020 Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2020-April:April Tidskriftsartikel (refereegranskat)
18.	Chen, Shuangshuang, 1992-, et al. (författare) Amortized Variational Inference for Road Friction Estimation 2020 Ingår i: 2020 IEEE Intelligent Vehicles Symposium (IV). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1777-1784, s. 1777-1784 Konferensbidrag (refereegranskat)abstract Road friction estimation concerns inference of the coefficient between the tire and road surface to facilitate active safety features. Current state-of-the-art methods lack generalization capability to cope with different tire characteristics and models are restricted when using Bayesian inference in estimation while recent supervised learning methods lack uncertainty prediction on estimates. This paper introduces variational inference to approximate intractable posterior of friction estimates and learns an amortized variational inference model from tire measurement data to facilitate probabilistic estimation while sustaining the flexibility of tire models. As a by-product, a probabilistic tire model can be learned jointly with friction estimator model. Experiments on simulated and field test data show that the learned friction estimator provides accurate estimates with robust uncertainty measures in a wide range of tire excitation levels. Meanwhile, the learned tire model reflects well-studied tire characteristics from field test data.
19.	Chen, Shuangshuang, 1992-, et al. (författare) Monte Carlo Filtering Objectives 2021 Ingår i: IJCAI International Joint Conference on Artificial Intelligence. - : International Joint Conferences on Artificial Intelligence. - 1045-0823. ; , s. 2256-2262 Konferensbidrag (refereegranskat)abstract Learning generative models and inferring latent trajectories have shown to be challenging for time series due to the intractable marginal likelihoods of flexible generative models. It can be addressed by surrogate objectives for optimization. We propose Monte Carlo filtering objectives (MCFOs), a family of variational objectives for jointly learning parametric generative models and amortized adaptive importance proposals of time series. MCFOs extend the choices of likelihood estimators beyond Sequential Monte Carlo in state-of-the-art objectives, possess important properties revealing the factors for the tightness of objectives, and allow for less biased and variant gradient estimates. We demonstrate that the proposed MCFOs and gradient estimations lead to efficient and stable model learning, and learned generative models well explain data and importance proposals are more sample efficient on various kinds of time series data.
20.	Colledanchise, Michele (författare) Behavior Trees in Robotics 2017 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Behavior Trees (BTs) are a Control Architecture (CA) that was invented in the video game industry, for controlling non-player characters. In this thesis we investigate the possibilities of using BTs for controlling autonomous robots, from a theoretical as well as practical standpoint. The next generation of robots will need to work, not only in the structured assembly lines of factories, but also in the unpredictable and dynamic environments of homes, shops, and other places where the space is shared with humans, and with different and possibly conflicting objectives. The nature of these environments makes it impossible to first compute the long sequence of actions needed to complete a task, and then blindly execute these actions. One way of addressing this problem is to perform a complete re-planning once a deviation is detected. Another way is to include feedback in the plan, and invoke additional incremental planning only when outside the scope of the feedback built into the plan. However, the feasibility of the latter option depends on the choice of CA, which thereby impacts the way the robot deals with unpredictable environments. In this thesis we address the problem of analyzing BTs as a novel CA for robots. The philosophy of BTs is to create control policies that are both modular and reactive. Modular in the sense that control policies can be separated and recombined, and reactive in the sense that they efficiently respond to events that were not predicted, either caused by external agents, or by unexpected outcomes of robot's own actions. Firstly, we propose a new functional formulation of BTs that allows us to mathematically analyze key system properties using standard tools from robot control theory. In particular we analyze whenever a BT is safe, in terms of avoiding particular parts of the state space; and robust, in terms of having a large domain of operation. This formulation also allows us to compare BTs with other commonly used CAs such as Finite State Machines (FSMs); the Subsumption Architecture; Sequential Behavior Compositions; Decision Trees; AND-OR Trees; and Teleo-Reactive Programs. Then we propose a framework to systematically analyze the efficiency and reliability of a given BT, in terms of expected time to completion and success probability. By including these performance measures in a user defined objective function, we can optimize the order of different fallback options in a given BT for minimizing such function. Finally we show the advantages of using BTs within an Automated Planning framework. In particular we show how to synthesize a policy that is reactive, modular, safe, and fault tolerant with two different approaches: model-based (using planning), and model-free (using learning).
21.	Cruciani, Silvia, 1991-, et al. (författare) Discrete Bimanual Manipulation for Wrench Balancing Annan publikation (övrigt vetenskapligt/konstnärligt)abstract Dual-arm robots can overcome grasping force and payload limitations of a single arm by jointly grasping an object.However, if the distribution of mass of the grasped object is not even, each arm will experience different wrenches that can exceed its payload limits.In this work, we consider the problem of balancing the wrenches experienced by a dual-arm robot grasping a rigid tray.The distribution of wrenches among the robot arms changes due to objects being placed on the tray.We present an approach to reduce the wrench imbalance among arms through discrete bimanual manipulation.Our approach is based on sequential sliding motions of the grasp points on the surface of the object, to attain a more balanced configuration.%This is achieved in a discrete manner, one arm at a time, to minimize the potential for undesirable object motion during execution.We validate our modeling approach and system design through a set of robot experiments.
22.	Cruciani, Silvia, 1991-, et al. (författare) Discrete Bimanual Manipulation for Wrench Balancing 2020 Ingår i: 2020 IEEE International Conference on Robotics and Automation, ICRA 2020. - : Institute of Electrical and Electronics Engineers Inc.. - 1050-4729 .- 2577-087X. - 9781728173955 ; , s. 2631-2637 Konferensbidrag (refereegranskat)abstract Dual-arm robots can overcome grasping force and payload limitations of a single arm by jointly grasping an object. However, if the distribution of mass of the grasped object is not even, each arm will experience different wrenches that can exceed its payload limits. In this work, we consider the problem of balancing the wrenches experienced by a dual-arm robot grasping a rigid tray. The distribution of wrenches among the robot arms changes due to objects being placed on the tray. We present an approach to reduce the wrench imbalance among arms through discrete bimanual manipulation. Our approach is based on sequential sliding motions of the grasp points on the surface of the object, to attain a more balanced configuration. We validate our modeling approach and system design through a set of robot experiments.
23.	Cuiral Zueco, Ignacio, et al. (författare) Contour Based Object-Compliant Shape Control 2023 Ingår i: IEEE Robotics and Automation Letters. - 2377-3766. ; 8:8, s. 5164-5171 Tidskriftsartikel (refereegranskat)abstract Shape control strategies seek to bring deformable objects towards a desired target shape. However, conventional methods focus on reaching the target shape without considering the extent to which the object is deformed during the control process. Control actions may generate unnecessary deformations and thus, increase the possibility of object over-stressing and failure. In this letter, we tackle the problem of vision-based object-compliant shape control (OCSC) with focus on 2D contours of texture-less objects. We propose a novel shape control framework that makes use of a multi-scale analysis of the contour's length and curvature to reduce the amount of deformation objects need to undergo during the shape control task. We evaluate our approach with simulations and experiments.
24.	Dahlin, Albin, 1992, et al. (författare) Adaptive Trajectory Generation under Velocity Constraints using Dynamical Movement Primitives 2020 Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 4:2, s. 438-443 Tidskriftsartikel (refereegranskat)abstract IEEE This letter addresses the problem of adaptive trajectory generation under velocity constraints while preserving the desired path shape. We adopt the framework of Dynamical Movement Primitives (DMPs) for trajectory modeling that offers useful features for online trajectory modulation using spatial and temporal parameter adaptation. This paper proposes a temporal coupling for DMPs based on a repulsive potential that keeps the velocity within predefined limits while inherently ensuring path shape invariance. The performance and stability of the proposed method are proven by Lyapunov-like arguments, and simulations are presented to verify the result.
25.	Dahlin, Albin, 1992, et al. (författare) Creating Star Worlds: Reshaping the Robot Workspace for Online Motion Planning 2023 Ingår i: IEEE Transactions on Robotics. - 1552-3098 .- 1941-0468. ; 39:5, s. 3655-3670 Tidskriftsartikel (refereegranskat)abstract Closed-loop motion planning is suitable for obstacle avoidance in dynamically changing environments due to its reactive nature, and various methods have been presented to provide (almost) global convergence. A common assumption in the control design is that the robot operates in a disjoint star world, i.e., all obstacles are strictly starshaped and mutually disjoint. However, in real-life scenarios obstacles may intersect due to expanded obstacle regions corresponding to robot radius or safety margins. To broaden the applicability of closed-loop motion planning methods, such as harmonic potential fields, we propose a method to reshape a workspace of intersecting obstacles into a disjoint star world. The algorithm is based on two novel concepts presented here, namely, admissible kernel and starshaped hull with specified kernel, which are closely related to the notion of starshaped hull. The utilization of the proposed method is illustrated with examples of a robot operating in a 2-D workspace using a harmonic potential field approach in combination with the developed algorithm.
26.	Dahlin, Albin, 1992, et al. (författare) Obstacle Avoidance in Dynamic Environments via Tunnel-following MPC with Adaptive Guiding Vector Fields 2023 Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 9798350301243 ; 2023, s. 5784-5789 Konferensbidrag (refereegranskat)abstract This paper proposes a motion control scheme for robots operating in a dynamic environment with concave obstacles. A Model Predictive Controller (MPC) is constructed to drive the robot towards a goal position while ensuring collision avoidance without direct use of obstacle information in the optimization problem. This is achieved by guaranteeing tracking performance of an appropriately designed receding horizon path. The path is computed using a guiding vector field defined in a subspace of the free workspace where each point in the subspace satisfies a criteria for minimum distance to all obstacles. The effectiveness of the control scheme is illustrated by means of simulation.
27.	Dahlin, Albin, 1992, et al. (författare) Temporal Coupling of Dynamical Movement Primitives for Constrained Velocities and Accelerations 2021 Ingår i: IEEE Robotics and Automation Letters. - 2377-3766. ; 6:2, s. 2233-2239 Tidskriftsartikel (refereegranskat)abstract The framework of Dynamical Movement Primitives (DMPs) has become a popular method for trajectory generation in robotics. Most robotic systems are subject to saturation and/or kinematic constraints on motion variables, but DMPs do not inherently encode constraints and this may lead to poor tracking performance. Temporal coupling (online temporal scaling) of DMPs represents a possible way for handling constrained systems. This letter presents a temporal coupling for DMPs to handle velocity and acceleration constraints for the generated trajectory. A novel filter is presented based on a potential function which proactively scales the trajectory before reaching the acceleration limits. In this way, the velocities and accelerations remain within the limits even for trajectories with aggressive accelerations and stricter bounds. The performance of the proposed method is demonstrated by means of simulations and experiments on a UR10 robot.
28.	Dahlin, Albin, 1992, et al. (författare) Trajectory Scaling for Reactive Motion Planning 2022 Ingår i: Proceedings - IEEE International Conference on Robotics and Automation. - 1050-4729. ; , s. 5242-5248 Konferensbidrag (refereegranskat)abstract Trajectory scaling has long been used to address velocity and acceleration constraints in robotic motion planning. In later years, reactive motion planning based on dynamical systems has become popular. The traditional scaling techniques are not always suitable to adopt directly when online modifications of the trajectories are made leading to feasibility problems. In this paper, we propose an approach which scales trajectories modelled as dynamical systems for improved feasibility. This is achieved by proactively scaling the trajectory as the acceleration limits are approached. Performance is illustrated by means of simulations and experiments on a UR10 robot.
29.	Diogo, Almeida, et al. (författare) Dexterous manipulation by means of compliant grasps and external contacts 2017 Ingår i: 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS). ; , s. 1913-1920 Konferensbidrag (refereegranskat)
30.	Doulgeri, Zoe, et al. (författare) An Adaptive Force Regulator for a Robot in Compliant Contact with an Unknown Surface 2005 Ingår i: 2005 IEEE International Conference on Robotics and Automation (ICRA), Vols 1-4. ; , s. 2685-2690 Konferensbidrag (refereegranskat)abstract This paper refers to the problem of force regulation for a robot finger with soft tip in contact with a rigid surface with unknown geometrical characteristics. A simple adaptive controller is employed in order to cope with surface kinematic uncertainties and the asymptotic stability of the force error is shown for the spatial case. Simulation results demonstrate the controller performance.
31.	Doulgeri, Zoe, et al. (författare) An adaptive law for slope identification, position tracking and force regulation for a robot in compliant contact with an unknown surface 2007 Ingår i: Mediterranean Conference on Control & Automation, 2007. MED '07.. - 9781424412815 ; , s. 52-57 Konferensbidrag (refereegranskat)abstract This work deals with the problem of force regulation and position trajectory tracking for a robot in compliant contact under kinematic uncertainties. A robotic finger with a soft hemispherical tip of uncertain compliance is considered in contact with a rigid flat surface of unknown position and orientation. A novel adaptive controller is proposed and is proved to achieve the convergence of force and position errors to zero by identifying the slope given a persistently excited desired velocity. The performance of the proposed controller is demonstrated by a simulation example.
32.	Doulgeri, Zoe, et al. (författare) Force position control for a robot finger with a soft tip and kinematic uncertainties 2007 Ingår i: Robotics and Autonomous Systems. - : Elsevier BV. - 0921-8890 .- 1872-793X. ; 55:4, s. 328-336 Tidskriftsartikel (refereegranskat)abstract We consider the problem of force and position regulation for a robot finger with a soft tip in contact with a surface with unknown geometrical characteristics. An adaptive controller is proposed, and the asymptotic convergence of the applied force error and the estimated position error of the tip to zero is shown for the spatial case. Simulation results demonstrate the controller performance.
33.	Doulgeri, Zoe, et al. (författare) Force/position control self-tuned to unknown surface slopes using motion variables 2008 Ingår i: Robotica (Cambridge. Print). - : Cambridge University Press. - 0263-5747 .- 1469-8668. ; 26:6, s. 703-710 Tidskriftsartikel (refereegranskat)abstract This work considers the problem of force/position regulationfor a robotic ﬁnger in compliant contact with an unknowncurved surface resulting in uncertain force and positioncontrol subspaces. The proposed controller is an adaptivecontrol scheme of a simple structure that achieves the desiredtarget by the on-line tuning of the position and force controlactions to their corresponding actual subspaces at the desiredpoint using motion state feedback. The local asymptoticstability of the system equilibrium point is proved and anestimate of the region of attraction is given. The controllerperformance is illustrated by a simulation example.
34.	Doulgeri, Zoe, et al. (författare) Force/Position Regulation for a Robot in Compliant Contact Using Adaptive Surface Slope Identification 2008 Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 53:9, s. 2116-2122 Tidskriftsartikel (refereegranskat)abstract This work proposes a control law for the force position regulation problem under surface kinematic uncertainties. A compliant contact with friction is considered. The control law achieves exact regulation of force and position along the surface tangent by identifying the uncertain surface slope without any force, tactile and/or vision sensory requirements. The asymptotic stability of the closed loop system equilibrium point is proved in a local sense and is demonstrated by a simulation example.
35.	Doulgeri, Zoe, et al. (författare) Performance analysis of a soft tip robotic finger controlled by a parallel force/position regulator under kinematic uncertainties 2007 Ingår i: IET Control Theory & Applications. - : Institution of Engineering and Technology (IET). - 1751-8644 .- 1751-8652. ; 1:1, s. 273-280 Tidskriftsartikel (refereegranskat)abstract The performance of a modiﬁed parallel control scheme is examined under surfacekinematic uncertainties using nonlinear stability analysis. The controlled system is a roboticﬁnger with a soft hemispherical ﬁngertip of signiﬁcant radius in contact with an unknownsurface. Analysis of the control system performance shows that force converges to the desiredvalue, whereas position errors stay close to zero and in some cases can even vanish despite uncertainties. Simulation results support the theoretical ﬁndings and illustrate the performance of theproposed controller.
36.	Doulgeri, Zoe, et al. (författare) PID type robot joint position regulation with prescribed performance guaranties 2010 Ingår i: 2010 IEEE International Conference on Robotics and Automation (ICRA). - : IEEE Robotics and Automation Society. - 9781424450404 ; , s. 4137-4142 Konferensbidrag (refereegranskat)abstract This paper proposes a PID type regulator that achieves not only the global asymptotic convergence of the robot joint velocities and position errors to zero but it also guarantees a prescribed performance for the position error transient that is independent of system constants and control parameters. The proportional term of the control input uses a transformed error (TP) which incorporates the desired performance function; given sufficiently high proportional and damping gains, the proposed TPID controller ensures the position error's prescribed performance irrespective of constant disturbances and choice of control gains. Control parameter selection is merely confined in achieving admissible input torques. Simulation results for a three dof spatial robot confirm the theoretical analysis and illustrate the robustness of the prescribed performance regulator in case of time-variant bounded disturbances.
37.	Doulgeri, Zoe, et al. (författare) Prescribed performance control for robot joint trajectory tracking under parametric and model uncertainties 2009 Ingår i: 17th Mediterranean Conference on Control and Automation, 2009. MED'09. - : VDE Verlag GmbH. - 9781424446841 ; , s. 1313-1318 Konferensbidrag (refereegranskat)abstract This work proposes a control law for the robot joint trajectory tracking in free space that achieves a prescribed performance of the joint position error under parametric uncertainties; the control law is extended for the case of bounded disturbances. A performance function incorporating predefined performance indices is used to produce a transformed error that is injected in the controller. Furthermore, asymptotic stability of the velocity error in case of zero disturbances and uniformly ultimate boundedness in an arbitrarily small region for bounded disturbances is achieved. Simulation results confirm the theoretical findings and compare the proposed controller with a conventional one.
38.	Droukas, Leonidas, et al. (författare) Force/Position/Rolling Control For Spherical Tip Robotic Fingers 2015 Ingår i: IEEE International Conference on Intelligent Robots and Systems. - 2153-0858 .- 2153-0866. - 9781479999941 ; 2015-December, s. 858-863 Konferensbidrag (refereegranskat)abstract The rolling motion of a soft robotic fingertip is in this paper explicitly included in the control objectives together with the force/position regulation targets. A model based control law is proposed to linearize and decouple the system with respect to the force/position and sliding dynamics based on an appropriately defined task Jacobian. The controller is validated by simulations including rolling on a stationary surface and graspless manipulation of a flat object.
39.	Hellander, Anja, 1996- (författare) On Optimal Integrated Task and Motion Planning with Applications to Tractor-Trailers 2023 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract An important aspect in autonomous systems is the ability of a system to plan before acting. This includes both high-level task planning to determine what sequence of actions to take in order for the system to reach a goal state, as well as low-level motion planning to detail how to perform the actions required.While it is sometimes possible to plan hierarchically, i.e., to first compute a task plan and then compute motion plans for each action in the task plan, there are also many problem instances where this approach fails to find a feasible plan as not all task plans lead to motion-planning problems that have feasible solutions. For this reason, it is desirable to solve the two problems jointly rather than sequentially. Additionally, it is often desirable to find plans that optimize a performance measure, such as the energy used, the length of the path travelled by the system or the time required. This thesis focuses on the problem of finding joint task and motion plans that optimize a performance measure.The first contribution is a method for solving a joint task and motion planning problem, that can be formulated as a traveling salesman problem with dynamic obstacles and motion constraints, to resolution optimality. The proposed method uses a planner comprising two nested graph-search planners. Several different heuristics are considered and evaluated.The second contribution is a method for solving a joint task and motion planning problem, in the form of a rearrangement problem for a tractor-trailer system, to resolution optimality. The proposed method combines a task planner with motion planners, all based on heuristically guided graph search, and uses branch-and-bound techniques in order to improve the efficiency of the search algorithm.The final contribution is a method for improving task and motion plans for rearrangement problems using optimal control. The proposed method takes inspiration from finite-horizon optimal control and decomposes the optimization problem into several smaller optimization problems rather than solving one larger optimization problem. Compared to solving the original larger optimization problem, it is demonstrated that this can lead to reduced computation time without any significant decrease in solution quality.
40.	Jaberzadeh Ansari, Ramin, 1987, et al. (författare) Human grasp position estimation for human–robot cooperative object manipulation 2020 Ingår i: Robotics and Autonomous Systems. - : Elsevier BV. - 0921-8890. ; 131 Tidskriftsartikel (refereegranskat)abstract This paper addresses the problem of human grasp position estimation in a physical human–robot object handling scenario. The problem is formulated as a linear regression by considering the human grasp position and their exerted torque as unknown parameters. We propose a modified least-squares algorithm to estimate the parameters by evaluating the quality of the estimates based on the assumption that the parameters should remain constant for a period of time. The solution is model-agnostic in terms of the human force/torque model – requiring only force/torque measurements on the robot side and proprioception – and is model-based in terms of the object model. The proposed grasp position estimation method is compared statistically with a conventional contact point estimation method using the collected experimental data. Moreover, the performance of the developed method is evaluated through various scenarios of physical human–robot interaction.
41.	Jaberzadeh Ansari, Ramin, 1987, et al. (författare) Physical Human-Robot Interaction through a Jointly-held Object based on Kinesthetic Perception 2018 Ingår i: RO-MAN 2018 - 27th IEEE International Symposium on Robot and Human Interactive Communication. ; , s. 1099-1104 Konferensbidrag (refereegranskat)abstract This paper deals with the problem of human-robot cooperative object manipulation for cases where the grasp position of the operator can change during task execution similar to human-human collaborative scenarios. In state of the art algorithms for cooperative object handling, a constant grasping position is considered for the operator. In order to accommodate the changes of the human grasping point in the control design, we do not depend on sensors on the operator's hand or on the object but we employ estimates obtained through a recursive least-squares estimator. The estimation algorithm uses only the measured wrenches obtained by a force/torque sensor located at the end-effector of the manipulator. We also propose a switching strategy for a damping controller based on the online estimates. Simulation results are provided in order to demonstrate the proposed method.
42.	Jaberzadeh Ansari, Ramin, 1987, et al. (författare) Reducing the human effort for human-robot cooperative object manipulation via control design 2017 Ingår i: IFAC PAPERSONLINE. - : ELSEVIER SCIENCE BV. - 2405-8963. ; , s. 14922-14927 Konferensbidrag (refereegranskat)abstract This study is concerned with the shared object manipulation problem in a physical Human-Robot Interaction (pHRI) setting. In such setups, the operator manipulates the object with the help of a robot. In this paper, the operator is assigned with the lead role, and the robot is passively following the forces/torques exerted by the operator. We propose a controller that is free from the well-known translation/rotation problem and enhances the operator's ability to move the object by reducing the human effort. The key point in our study is that the controller is defined based on the instantaneous center of rotation. The passivity of the system including the object and the manipulator has been evaluated. Simulation results validate the theoretical findings on different scenarios of subsequent rotations and translations of the object.
43.	Jaberzadeh Ansari, Ramin, 1987, et al. (författare) Task-based role adaptation for human-robot cooperative object handling 2021 Ingår i: IEEE Robotics and Automation Letters. - 2377-3766. ; 6:2, s. 3592-3598 Tidskriftsartikel (refereegranskat)abstract In this letter, we propose a task-based role allocation control scheme for cooperative manipulation of a rigid-body object jointly held by a human and a robot. The task-based allocation scheme allows an assistive robot to take an active role when the task is known. To deal with the translation/rotation problem, we define rotation and translation as distinct parameterized tasks. The task that describes better human intention is identified by solving an optimization problem with a predefined adjustable similarity factor for each task. The role of the robot while performing the identified task can be directly tuned as a parameter associated with the percentage of the required force for performing the corresponding task and is predefined for each task and degree of freedom, independently. The performance of the proposed control scheme is evaluated via simulation and experiments on a real robot setup.
44.	Karayiannidis, Yiannis, 1980-, et al. (författare) A Model-Free Controller for Guaranteed Prescribed Performance Tracking of Both Robot Joint Positions and Velocities 2016 Ingår i: IEEE Robotics and Automation Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2377-3766. ; 1:1, s. 267-273 Tidskriftsartikel (refereegranskat)abstract The problem of robot joint position and velocity tracking with prescribed performance guarantees is considered. The proposed controller is able to guarantee a prescribed transient and steady state behavior for the position and the velocity tracking errors without utilizing either the robot dynamic model or any approximation structures. Its performance is demonstrated and assessed via experiments with a KUKA LWR4+ arm.
45.	Karayiannidis, Yiannis, 1980-, et al. (författare) A neuro-adaptive controller for the force/position tracking of a robot manipulator under model uncertainties in compliance and friction 2006 Ingår i: Proceedings of 2006 Mediterranean Conference on Control and Automation, Vols 1 and 2. - NEW YORK : IEEE. - 9780978672010 ; , s. 75-80 Konferensbidrag (refereegranskat)abstract In this work, we consider the force and position trajectory tracking for a robot manipulator in compliant contact with a surface in the presence of unknown stiffness and dynamic friction. A novel neuro-adaptive controller is proposed that exploits the approximation capabilities of the linear in the weights neural networks and the uniform ultimate boundedness of force and position error is proved. Simulation results illustrate the performance of the proposed controller.
46.	Karayiannidis, Yiannis, 1980-, et al. (författare) Adaptive control for frictional robot contact tasks on uncertain surface slopes 2008 Ingår i: 2008 MEDITERRANEAN CONFERENCE ON CONTROL AUTOMATION, VOLS 1-4. - NEW YORK : IEEE. - 9781424425044 ; , s. 1300-1305 Konferensbidrag (refereegranskat)abstract In robot constrained motion problems with frictional contacts, uncertainties on the contacted surface slope distort control targets and affect the control system performance. The surface normal direction cosines are in this case uncertain parameters that are involved in both the control law and the control targets. This work proposes an adaptive controller that achieves the desired goal given a persistently excited tip velocity magnitude on the surface by achieving the convergence of the estimated direction parameters to their actual values. The controller requires measurements of total force and joint variables. A simulation example for a 6 d.o.f. robot is used to illustrate the theoretical results.
47.	Karayiannidis, Yiannis, 1980-, et al. (författare) Adaptive control of robot contact tasks with on-line learning of planar surfaces 2009 Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 45:10, s. 2374-2382 Tidskriftsartikel (refereegranskat)abstract In robot constrained motion problems on planar surfaces with frictional contacts, uncertainties on the contacted surface not only affect the control system performance but also distort control targets. The surface normal direction cosines are in this case uncertain parameters that are involved in both the control law and the control targets. This work proposes an adaptive learning controller that uses force and joint position/velocity measurements to simultaneously learn the surface orientation and achieve the desired goal. Simulation examples for a 6 dof robot are used to illustrate the theoretical results and the performance of the proposed controller in practical cases.
48.	Karayiannidis, Yiannis, 1980-, et al. (författare) Adaptive force/velocity control for opening unknown doors 2012 Ingår i: Robot Control, Volume 10, Part 1. - 9783902823113 ; , s. 753-758 Konferensbidrag (refereegranskat)abstract The problem of door opening is fundamental for robots operating in domesticenvironments. Since these environments are generally unstructured, a robot must deal withseveral types of uncertainties associated with the dynamics and kinematics of a door to achievesuccessful opening. The present paper proposes a dynamic force/velocity controller which usesadaptive estimation of the radial direction based on adaptive estimates of the door hinge’sposition. The control action is decomposed into estimated radial and tangential directions,which are proved to converge to the corresponding actual values. The force controller usesreactive compensation of the tangential forces and regulates the radial force to a desired smallvalue, while the velocity controller ensures that the robot’s end-effector moves with a desiredtangential velocity. The performance of the control scheme is demonstrated in simulation witha 2 DoF planar manipulator opening a door.
49.	Karayiannidis, Yiannis, et al. (författare) An Adaptive Control Approach for Opening Doors and Drawers Under Uncertainties 2016 Ingår i: IEEE Transactions on robotics. - : IEEE. - 1552-3098 .- 1941-0468. ; 32:1, s. 161-175 Tidskriftsartikel (refereegranskat)abstract We study the problem of robot interaction with mechanisms that afford one degree of freedom motion, e.g., doors and drawers. We propose a methodology for simultaneous compliant interaction and estimation of constraints imposed by the joint. Our method requires no prior knowledge of the mechanisms' kinematics, including the type of joint, prismatic or revolute. The method consists of a velocity controller that relies on force/torque measurements and estimation of the motion direction, the distance, and the orientation of the rotational axis. It is suitable for velocity controlled manipulators with force/torque sensor capabilities at the end-effector. Forces and torques are regulated within given constraints, while the velocity controller ensures that the end-effector of the robot moves with a task-related desired velocity. We give proof that the estimates converge to the true values under valid assumptions on the grasp, and error bounds for setups with inaccuracies in control, measurements, or modeling. The method is evaluated in different scenarios involving opening a representative set of door and drawer mechanisms found in household environments.
50.	Karayiannidis, Yiannis, 1980, et al. (författare) An Adaptive Control Approach for Opening Doors and Drawers Under Uncertainties 2016 Ingår i: IEEE Transactions on Robotics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1552-3098 .- 1941-0468. ; 32:1, s. 161-175 Tidskriftsartikel (refereegranskat)abstract We study the problem of robot interaction with mechanisms that afford one degree of freedom motion, e.g., doors and drawers. We propose a methodology for simultaneous compliant interaction and estimation of constraints imposed by the joint. Our method requires no prior knowledge of the mechanisms' kinematics, including the type of joint, prismatic or revolute. The method consists of a velocity controller that relies on force/torque measurements and estimation of the motion direction, the distance, and the orientation of the rotational axis. It is suitable for velocity controlled manipulators with force/torque sensor capabilities at the end-effector. Forces and torques are regulated within given constraints, while the velocity controller ensures that the end-effector of the robot moves with a task-related desired velocity. We give proof that the estimates converge to the true values under valid assumptions on the grasp, and error bounds for setups with inaccuracies in control, measurements, or modeling. The method is evaluated in different scenarios involving opening a representative set of door and drawer mechanisms found in household environments.

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