14 research outputs found

    ๋ถˆํ™•์‹ค์„ฑ์„ ํฌํ•จํ•˜๋Š” ์กฐ๋ฆฝ์ž‘์—…์„ ์œ„ํ•œ ์ปดํ”Œ๋ผ์ด์–ธ์Šค ๊ธฐ๋ฐ˜ ํŽ™์ธํ™€ ์ „๋žต

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ) -- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ์œตํ•ฉ๊ณผํ•™๊ธฐ์ˆ ๋Œ€ํ•™์› ์œตํ•ฉ๊ณผํ•™๋ถ€(์ง€๋Šฅํ˜•์œตํ•ฉ์‹œ์Šคํ…œ์ „๊ณต), 2020. 8. ๋ฐ•์žฌํฅ.The peg-in-hole assembly is a representative robotic task that involves physical contact with the external environment. The strategies generally involve performing the assembly task by estimating the contact state between the peg and the hole. The contact forces and moments, measured using force sensors, are primarily used to estimate the contact state. In this paper, in contrast to past research in the area, which has involved the utilization of such expensive devices as force/torque sensors or remote compliance mechanisms, an inexpensive method is proposed for peg-in-hole assembly without force feedback or passive compliance mechanisms. The method consists of an analysis of the state of contact between the peg and the hole as well as a strategy to overcome the inevitable positional uncertainty of the hole incurred in the recognition process. A control scheme was developed to yield compliant behavior from the robot with physical contact under the condition of hybrid position/force control. Proposed peg-in-hole strategy is based on compliance characteristics and generating the force and moment. The peg is inserted into the hole as it adapts to the external environment. The effectiveness of the proposed method was experimentally verified using a humanoid upper body robot with fifty degrees of freedom and a peg-in-hole apparatus with a small clearance (0.1 mm). Three cases of experiments were conducted; Assembling the peg attached to the arm in the hole fixed in the external environment, grasping a peg with an anthropomorphic hand and assembling it into a fixed hole, and grasping both peg and hole with both hands and assembling each other. In order to assemble the peg-in-hole through the proposed strategy by the humanoid upper body robot, I present a method of gripping an object, estimating the kinematics of the gripped object, and manipulating the gripped object. In addition to the cost aspect, which is the fundamental motivation for the proposed strategy, the experimental results show that the proposed strategy has advantages such as fast assembly time and high success rate, but has the disadvantage of unpredictable elapsed time. The reason for having a high variance value for the success time is that the spiral trajectory, which is most commonly used, is used. In this study, I analyze the efficiency of spiral force trajectory and propose an improved force trajectory. The proposed force trajectory reduces the distribution of elapsed time by eliminating the uncertainty in the time required to find a hole. The efficiency of the force trajectory is analyzed numerically, verified through repeated simulations, and verified by the actual experiment with humanoid upper body robot developed by Korea institute of industrial technology.ํŽ™์ธํ™€ ์กฐ๋ฆฝ์€ ๋กœ๋ด‡์˜ ์ ‘์ด‰ ์ž‘์—…์„ ๋Œ€ํ‘œํ•˜๋Š” ์ž‘์—…์œผ๋กœ, ํŽ™์ธํ™€ ์กฐ๋ฆฝ ์ „๋žต์„ ์—ฐ๊ตฌํ•จ์œผ๋กœ์จ ์‚ฐ์—… ์ƒ์‚ฐ ๋ถ„์•ผ์˜ ์กฐ๋ฆฝ์ž‘์—…์— ์ ์šฉํ•  ์ˆ˜ ์žˆ๋‹ค. ํŽ™์ธํ™€ ์กฐ๋ฆฝ์ž‘์—…์€ ์ผ๋ฐ˜์ ์œผ๋กœ ํŽ™๊ณผ ํ™€ ๊ฐ„์˜ ์ ‘์ด‰์ƒํƒœ๋ฅผ ์ถ”์ •ํ•จ์œผ๋กœ์จ ์ด๋ฃจ์–ด์ง„๋‹ค. ์ ‘์ด‰์ƒํƒœ๋ฅผ ์ถ”์ •ํ•˜๊ธฐ ์œ„ํ•ด ๊ฐ€์žฅ ๋„๋ฆฌ ์“ฐ์ด๋Š” ๋ฐฉ๋ฒ•์€ ํž˜ ์„ผ์„œ๋ฅผ ์‚ฌ์šฉํ•˜๋Š” ๊ฒƒ์ธ๋ฐ, ์ ‘์ด‰ ํž˜๊ณผ ๋ชจ๋ฉ˜ํŠธ๋ฅผ ์ธก์ •ํ•˜์—ฌ ์ ‘์ด‰์ƒํƒœ๋ฅผ ์ถ”์ •ํ•˜๋Š” ๋ฐฉ์‹์ด๋‹ค. ๋งŒ์•ฝ ์ด๋Ÿฌํ•œ ์„ผ์„œ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š์„ ์ˆ˜ ์žˆ๋‹ค๋ฉด, ํ•˜๋“œ์›จ์–ด ๋น„์šฉ๊ณผ ์†Œํ”„ํŠธ์›จ์–ด ์—ฐ์‚ฐ๋Ÿ‰ ๊ฐ์†Œ ๋“ฑ์˜ ์žฅ์ ์ด ์žˆ์Œ์€ ์ž๋ช…ํ•˜๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ํž˜ ์„ผ์„œ ํ˜น์€ ์ˆ˜๋™ ์ปดํ”Œ๋ผ์ด์–ธ์Šค ์žฅ์น˜๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š๋Š” ํŽ™์ธํ™€ ์ „๋žต์„ ์ œ์•ˆํ•œ๋‹ค. ํ™€์— ๋Œ€ํ•œ ์ธ์‹ ์˜ค์ฐจ ํ˜น์€ ๋กœ๋ด‡์˜ ์ œ์–ด ์˜ค์ฐจ๋ฅผ ๊ทน๋ณตํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋จผ์ € ํŽ™๊ณผ ํ™€์˜ ์ ‘์ด‰ ๊ฐ€๋Šฅ ์ƒํƒœ๋ฅผ ๋ถ„์„ํ•˜๊ณ  ๋กœ๋ด‡์˜ ์ปดํ”Œ๋ผ์ด์–ธ์Šค ๋ชจ์…˜์„ ์œ„ํ•œ ์ œ์–ด ํ”„๋ ˆ์ž„์›Œํฌ๋ฅผ ๋””์ž์ธํ•œ๋‹ค. ์ „๋žต์€ ์ปดํ”Œ๋ผ์ด์–ธ์Šค ํŠน์ง•์— ๊ธฐ๋ฐ˜ํ•˜๋ฉฐ ํŽ™์— ํž˜๊ณผ ๋ชจ๋ฉ˜ํŠธ๋ฅผ ์ƒ์„ฑ์‹œํ‚ด์œผ๋กœ์จ ์กฐ๋ฆฝ์ž‘์—…์„ ์ˆ˜ํ–‰ํ•œ๋‹ค. ํŽ™์€ ์™ธ๋ถ€ํ™˜๊ฒฝ์— ์ˆœ์‘ํ•จ์œผ๋กœ์จ ํ™€์— ์‚ฝ์ž…๋œ๋‹ค. ์ œ์•ˆํ•œ ์ „๋žต์€ ๋‚ฎ์€ ๊ณต์ฐจ๋ฅผ ๊ฐ–๋Š” ํŽ™์ธํ™€ ์‹คํ—˜์„ ํ†ตํ•ด์„œ ๊ทธ ์œ ํšจ์„ฑ์ด ๊ฒ€์ฆ๋œ๋‹ค. ํŽ™๊ณผ ํ™€์„ ๋กœ๋ด‡ํŒ”๊ณผ ์™ธ๋ถ€ํ™˜๊ฒฝ์— ๊ฐ๊ฐ ๊ณ ์ •๋œ ํ™˜๊ฒฝ์—์„œ์˜ ์‹คํ—˜, ์ธ๊ฐ„ํ˜• ๋กœ๋ด‡ํ•ธ๋“œ๋ฅผ ์ด์šฉํ•˜์—ฌ ํŽ™์„ ์žก์•„์„œ ๊ณ ์ •๋œ ํ™€์— ์‚ฝ์ž…ํ•˜๋Š” ์‹คํ—˜, ๊ทธ๋ฆฌ๊ณ  ํ…Œ์ด๋ธ”์— ๋†“์ธ ํŽ™๊ณผ ํ™€์„ ๊ฐ๊ฐ ๋กœ๋ด‡ํ•ธ๋“œ๋กœ ํŒŒ์ง€ํ•˜์—ฌ ์กฐ๋ฆฝํ•˜๋Š” ์ด ์„ธ ๊ฐ€์ง€์˜ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ํ•ธ๋“œ๋กœ ํŽ™์„ ํŒŒ์ง€ํ•˜๊ณ  ์กฐ์ž‘ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ, ํŒŒ์ง€ ๋ฐฉ๋ฒ•๊ณผ ํ•ธ๋“œ๋ฅผ ์ด์šฉํ•œ ๋ฌผ์ฒด ์กฐ์ž‘ ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ๊ฐ„๋žตํžˆ ์†Œ๊ฐœํ•˜์˜€๋‹ค. ์ œ์•ˆํ•œ ์ „๋žต์˜ ์„ฑ๋Šฅ์„ ์‹คํ—˜์ ์œผ๋กœ ๋ถ„์„ํ•œ ๊ฒฐ๊ณผ, ๋†’์€ ์กฐ๋ฆฝ ์„ฑ๊ณต๋ฅ ์„ ๊ฐ–๋Š” ๋Œ€์‹  ์กฐ๋ฆฝ์‹œ๊ฐ„์ด ์˜ˆ์ธกํ•  ์ˆ˜ ์—†๋Š” ๋‹จ์ ์ด ๋‚˜ํƒ€๋‚˜ ์ด๋ฅผ ๋ณด์™„ํ•˜๊ธฐ ์œ„ํ•ด์„œ ๋ Œ์น˜ ๊ถค์  ๋˜ํ•œ ์ œ์•ˆํ•˜์˜€๋‹ค. ๋จผ์ € ๊ฐ€์žฅ ์ผ๋ฐ˜์ ์œผ๋กœ ์‚ฌ์šฉ๋˜๋Š” ๋‚˜์„  ํž˜ ๊ถค์ ์„ ์ด์šฉํ–ˆ์„ ๋•Œ ์กฐ๋ฆฝ ์„ฑ๊ณต์‹œ๊ฐ„์˜ ๋ถ„์‚ฐ์ด ํฐ ์ด์œ ๋ฅผ ํ™•๋ฅ ๊ฐœ๋…์„ ์ด์šฉํ•ด ๋ถ„์„ํ•˜๊ณ , ์ด๋ฅผ ๋ณด์™„ํ•˜๊ธฐ ์œ„ํ•œ ๋ถ€๋ถ„์  ๋‚˜์„  ํž˜ ๊ถค์ ์„ ์ œ์•ˆํ•œ๋‹ค. ์ œ์•ˆํ•œ ํž˜ ๊ถค์ ์ด ๋‚˜์„  ํž˜ ๊ถค์ ์— ๋น„ํ•ด ๊ฐ–๋Š” ์„ฑ๋Šฅ์˜ ์šฐ์ˆ˜์„ฑ์„ ์ฆ๋ช…ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ˆ˜์น˜์  ๋ถ„์„, ๋ฐ˜๋ณต์  ์‹œ๋ฎฌ๋ ˆ์ด์…˜, ๊ทธ๋ฆฌ๊ณ  ๋กœ๋ด‡์„ ์ด์šฉํ•œ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.1 INTRODUCTION 1 1.1 Motivation: Peg-in-Hole Assembly 1 1.2 Contributions of Thesis 2 1.3 Overview of Thesis 3 2 COMPLIANCE BASED STRATEGY 5 2.1 Background & Related Works 5 2.2 Analysis of Peg-in-Hole Procedure 6 2.2.1 Contact Analysis 7 2.2.2 Basic Idea 9 2.3 Peg-in-Hole Strategy 12 2.3.1 Unit Motions 12 2.3.2 State of Strategy 13 2.3.3 Conditions for State Transition 15 2.4 Control Frameworks 18 2.4.1 Control for Compliant Behavior 18 2.4.2 Friction Compensate 20 2.4.3 Control Input for the Strategy 25 2.5 Experiment 29 2.5.1 Experiment Environment 29 2.5.2 Fixed Peg and Fixed Hole 31 2.5.2.1 Experiment Results 31 2.5.2.2 Analysis of Force and Control Gain 36 2.5.3 Peg-in-Hole with Multi Finger Hand 41 2.5.3.1 Object Grasping 42 2.5.3.2 Object In-Hand Manipulation 44 2.5.3.3 Experiment Results 49 2.5.4 With Upper Body Robot 50 2.5.4.1 Peg-in-Hole Procedure 52 2.5.4.2 Kinematics of Grasped Object 54 2.5.4.3 Control Frameworks 54 2.5.4.4 Experiment Results 56 2.6 Discussion 59 2.6.1 Peg-in-Hole Transition 59 2.6.2 Influential Issues 59 3 WRENCH TRAJECTORY 63 3.1 Problem Statement 64 3.1.1 Hole Search Process 64 3.1.2 Spiral Force Trajectory Analysis 66 3.2 Partial Spiral Force Trajectory 70 3.2.1 Force Trajectory with Tilted Posture 70 3.2.2 Probability to Three-point Contact 76 3.3 SIMULATION & EXPERIMENT 78 3.3.1 Simulation 78 3.3.2 Experiment 83 4 CONCLUSIONS 90 Abstract (In Korean) 102Docto

    Robotic peg-hole insertion operation analysis.

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    Accomplishing task-invariant assembly strategies by means of an inherently accommodating robot arm

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    Despite the fact that the main advantage of robot manipulators was always meant to be their flexibility, they have not been applied widely to the assembly of industrial components in situations other than those where hard automation might be used. We identify the two main reasons for this as the 'fragility' of robot operation during tasks that involve contact, and the lack of an appropriate user interface. This thesis describes an attempt to address these problems.We survey the techniques that have been proposed to bring the performance of curยฌ rent industrial robot manipulators in line with expectations, and conclude that the main obstacle in realising a flexible assembly robot that exhibits robust and reliable behaviour is the problem of spatial uncertainty.Based on observations of the performance of position-controlled robot manipulators and what is involved during rigid-body part mating, we propose a model of assembly tasks that exploits the shape invariance of the part geometry across instances of a task. This allows us to escape from the problem of spatial uncertainty because we are 110 longer working in spatial terms. In addition, because the descriptions of assembly tasks that we derive are task-invariant, i.e. they are not dependent on part size or location, they lend themselves naturally to a task-level programming interface, thereby simplifying the process of programming an assembly robot.the process of programming an assembly robot. However, to test this approach empirically requires a manipulator that is able to control the force that it applies, as well as being sensitive to environmental constraints. The inertial properties of standard industrial manipulators preclude them from exhibiting this kind of behaviour. In order to solve this problem we designed and constructed a three degree of freedom, planar, direct-drive arm that is open-loop force-controllable (with respect to its end-point), and inherently accommodating during contact.In order to demonstrate the forgiving nature of operation of our robot arm we impleยฌ mented a generic crank turning program that is independent of the geometry of the crank involved, i.e. no knowledge is required of the location or length of the crank. I11 order to demonstrate the viability of our proposed approach to assembly we proยฌ grammed our robot system to perform some representative tasks; the insertion of a peg into a hole, and the rotation of a block into a corner. These programs were tested on parts of various size and material, and in various locations in order to illustrate their invariant nature.We conclude that the problem of spatial uncertainty is in fact an artefact of the fact that current industrial manipulators are designed to be position controlled. The work described in this thesis shows that assembly robots, when appropriately designed, controlled and programmed, can be the reliable and flexible devices they were always meant to be

    Stiffness Control in Robotic Assembly Tasks

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    The peg in hole problem has been heavily studied in literature as a simple model to analyze assembly scenarios. Due to advances in robotic hardware and research on robots which are safe to humans, many of the models and simplifications present in literature don't apply anymore or present poor approximations for modern robots with impedance controllers. In the following work the problem of a peg-in-hole insertion with a impedance controlled robot will be tackled, and simple rules to choose optimal cartesian stiffnesses are presented. The same rules are then applied to solve the problem of optimizing stiffnesses for a VSA robot, where a desired cartesian stiffness cannot generally be obtained. A method to chose weights for the simple weighted minimization of the distance between the desired and obtained cartesian stiffnesses is then proposed, and the results of both approaches are compared by using a robot with deboupled joint stiffness control. Lastly, results of a bimanual insertion using a real VSA robot are proposed

    ็›ธๅฏพๅบงๆจ™ใซใŠใ‘ใ‚‹้ซ˜้€Ÿ่ฆ–่ฆšใƒ•ใ‚ฃใƒผใƒ‰ใƒใƒƒใ‚ฏใซๅŸบใฅใใƒ€ใ‚คใƒŠใƒŸใƒƒใ‚ฏใ‚ณใƒณใƒšใƒณใ‚ปใƒผใ‚ทใƒงใƒณ

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    ๅญฆไฝใฎ็จฎๅˆฅ:่ชฒ็จ‹ๅšๅฃซUniversity of Tokyo(ๆฑไบฌๅคงๅญฆ

    Force sensing enhancement of robot system

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    At present there is a general industrial need to improve robot performance. Force feedback, which involves sensing and actuation, is one means of improving the relative position between the workpiece and the end-effector. In this research work various causes of errors and poor robot performance are identified. Several methods of improving the performance of robotic systems are discussed. As a result of this research, a system was developed which is interposed between the wrist and the gripper of the manipulator. This system integrates a force sensor with a micro-manipulator, via an electronic control unit, with a micro-computer to enhance a robot system. The force sensor, the micromanipulator and the electronic control unit, were all designed and manufactured at the robotic centre of Middlesex Polytechnic. The force feedback is provided by means of strain gauges and the associated bridge circuitry. Control algorithms which define the relationship between the force detected and the motion required are implemented in the software. The software is capable of performing two specific tasks in real time, these are: 1- Inserting a peg into a hole 2- Following an unknown geometric path A rig was designed and manufactured to enable the robot to follow different geometric shapes and paths in which force control was achieved mainly by control of the micro-manipulator

    Robotic learning of force-based industrial manipulation tasks

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    Even with the rapid technological advancements, robots are still not the most comfortable machines to work with. Firstly, due to the separation of the robot and human workspace which imposes an additional financial burden. Secondly, due to the significant re-programming cost in case of changing products, especially in Small and Medium-sized Enterprises (SMEs). Therefore, there is a significant need to reduce the programming efforts required to enable robots to perform various tasks while sharing the same space with a human operator. Hence, the robot must be equipped with a cognitive and perceptual capabilities that facilitate human-robot interaction. Humans use their various senses to perform tasks such as vision, smell and taste. One sensethat plays a significant role in human activity is โ€™touchโ€™ or โ€™forceโ€™. For example, holding a cup of tea, or making fine adjustments while inserting a key requires haptic information to achieve the task successfully. In all these examples, force and torque data are crucial for the successful completion of the activity. Also, this information implicitly conveys data about contact force, object stiffness, and many others. Hence, a deep understanding of the execution of such events can bridge the gap between humans and robots. This thesis is being directed to equip an industrial robot with the ability to deal with force perceptions and then learn force-based tasks using Learning from Demonstration (LfD).To learn force-based tasks using LfD, it is essential to extract task-relevant features from the force information. Then, knowledge must be extracted and encoded form the task-relevant features. Hence, the captured skills can be reproduced in a new scenario. In this thesis, these elements of LfD were achieved using different approaches based on the demonstrated task. In this thesis, four robotics problems were addressed using LfD framework. The first challenge was to filter out robotsโ€™ internal forces (irrelevant signals) using data-driven approach. The second robotics challenge was the recognition of the Contact State (CS) during assembly tasks. To tackle this challenge, a symbolic based approach was proposed, in which a force/torque signals; during demonstrated assembly, the task was encoded as a sequence of symbols. The third challenge was to learn a human-robot co-manipulation task based on LfD. In this case, an ensemble machine learning approach was proposed to capture such a skill. The last challenge in this thesis, was to learn an assembly task by demonstration with the presents of parts geometrical variation. Hence, a new learning approach based on Artificial Potential Field (APF) to learn a Peg-in-Hole (PiH) assembly task which includes no-contact and contact phases. To sum up, this thesis focuses on the use of data-driven approaches to learning force based task in an industrial context. Hence, different machine learning approaches were implemented, developed and evaluated in different scenarios. Then, the performance of these approaches was compared with mathematical modelling based approaches.</div

    Automated Assembly Using Feature Localization

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    Automated assembly of mechanical devices is studies by researching methods of operating assembly equipment in a variable manner; that is, systems which may be configured to perform many different assembly operations are studied. The general parts assembly operation involves the removal of alignment errors within some tolerance and without damaging the parts. Two methods for eliminating alignment errors are discussed: a priori suppression and measurement and removal. Both methods are studied with the more novel measurement and removal technique being studied in greater detail. During the study of this technique, a fast and accurate six degree-of-freedom position sensor based on a light-stripe vision technique was developed. Specifications for the sensor were derived from an assembly-system error analysis. Studies on extracting accurate information from the sensor by optimally reducing redundant information, filtering quantization noise, and careful calibration procedures were performed. Prototype assembly systems for both error elimination techniques were implemented and used to assemble several products. The assembly system based on the a priori suppression technique uses a number of mechanical assembly tools and software systems which extend the capabilities of industrial robots. The need for the tools was determined through an assembly task analysis of several consumer and automotive products. The assembly system based on the measurement and removal technique used the six degree-of-freedom position sensor to measure part misalignments. Robot commands for aligning the parts were automatically calculated based on the sensor data and executed

    Control and Learning of Compliant Manipulation Skills

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    Humans demonstrate an impressive capability to manipulate fragile objects without damaging them, graciously controlling the force and position of hands or tools. Traditionally, robotics has favored position control over force control to produce fast, accurate and repeatable motion. For extending the applicability of robotic manipulators outside the strictly controlled environments of industrial work cells, position control is inadequate. Tasks that involve contact with objects whose positions are not known with perfect certainty require a controller that regulates the relationship between positional deviations and forces on the robot. This problem is formalized in the impedance control framework, which focuses the robot control problem on the interaction between the robot and its environment. By adjusting the impedance parameters, the behavior of the robot can be adapted to the need of the task. However, it is often difficult to specify formally how the impedance should vary for best performance. Furthermore, fast it can be shown that careless variation of the impedance can lead to unstable regulation or tracking even in free motion. In the first part of the thesis, the problem of how to define a varying impedance for a task is addressed. A haptic human-robot interface that allows a human supervisor to teach impedance variations by physically interacting with the robot during task execution is introduced. It is shown that the interface can be used to enhance the performance in several manipulation tasks. Then, the problem of stable control with varying impedance is addressed. Along with a theoretical discussion on this topic, a sufficient condition for stable varying stiffness and damping is provided. In the second part of the thesis, we explore more complex manipulation scenarios via online generation of the robot trajectory. This is done along two axes 1) learning how to react to contact forces in insertion tasks which are crucial for assembly operations and 2) autonomous Dynamical Systems (DS) for motion representation with the capability to encode a family of trajectories rather than a fixed, time-dependent reference. A novel framework for task representation using DS is introduced, termed Locally Modulated Dynamical Systems (LMDS). LMDS differs from existing DS estimation algorithms in that it supports non-parametric and incremental learning all the while guaranteeing that the resulting DS is globally stable at an attractor point. To combine the advantages of DS motion generation with impedance control, a novel controller for tasks described by first order DS is proposed. The controller is passive, and has the properties of an impedance controller with the added flexibility of a DS motion representation instead of a time-indexed trajectory
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