55 research outputs found
Design, Development and Force Control of a Tendon-driven Steerable Catheter with a Learning-based Approach
In this research, a learning-based force control schema for tendon-driven steerable catheters with the application in robot-assisted tissue ablation procedures was proposed and validated. To this end, initially a displacement-based model for estimating the contact force between the catheter and tissue was developed. Afterward, a tendon-driven catheter was designed and developed. Next, a software-hardware-integrated robotic system for controlling and monitoring the pose of the catheter was designed and developed. Also, a force control schema was developed based on the developed contact force model as a priori knowledge. Furthermore, the position control of the tip of the catheter was performed using a learning-based inverse kinematic approach. By combining
the position control and the contact model, the force control schema was developed and validated. Validation studies were performed on phantom tissue as well as excised porcine tissue. Results of the validation studies showed that the proposed displacement-based model was 91.5% accurate in contact force prediction. Also, the system was capable of following a set of desired trajectories with an average root-mean-square error of less than 5%. Further validation studies revealed that the system could fairly generate desired static and dynamic force profiles on the phantom tissue. In summary, the proposed force control system did not necessitate the utilization of force sensors and could fairly contribute in automatizing the ablation task for robotic tissue ablation procedures
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Όλ¬Έ(λ°μ¬)--μμΈλνκ΅ λνμ :곡과λν κΈ°κ³ν곡곡νλΆ,2020. 2. μ΄λμ€.In this thesis, we present key theoretical components for realizing flying aerial skeleton system called LASDRA (large-size aerial skeleton with distributed rotor actuation). Aerial skeletons are articulated aerial robots actuated by distributed rotors including both ground connected type and flying type. These systems have recently attracted interest and are being actively researched in several research groups, with the expectation of applying those for aerial manipulation in distant/narrow places, or for the performance with entertaining purpose such as drone shows. Among the aerial skeleton systems, LASDRA system, proposed by our group has some significant advantages over the other skeleton systems that it is capable of free SE(3) motion by omni-directional wrench generation of each link, and also the system can be operated with wide range of configuration because of the 3DOF (degrees of freedom) inter-link rotation enabled by cable connection among the link modules.
To realize this LASDRA system, following three components are crucial: 1) a link module that can produce omni-directional force and torque and enough feasible wrench space; 2) pose and posture estimation algorithm for an articulated system with high degrees of freedom; and 3) a motion generation framework that can provide seemingly natural motion while being able to generate desired motion (e.g., linear and angular velocity) for the entire body. The main contributions of this thesis is theoretically developing these three components, and verifying these through outdoor flight experiment with a real LASDRA system. First of all, a link module for the LASDRA system is designed with proposed constrained optimization problem, maximizing the guaranteed feasible force and torque for any direction while also incorporating some constraints (e.g., avoiding inter-rotor air-flow interference) to directly obtain feasible solution. Also, an issue of ESC-induced (electronic speed control) singularity is first introduced in the literature which is inevitably caused by bi-directional thrust generation with sensorless actuators, and handled with a novel control allocation called selective mapping. Then for the state estimation of the entire LASDRA system, constrained Kalman filter based estimation algorithm is proposed that can provide estimation result satisfying kinematic constraint of the system, also along with a semi-distributed version of the algorithm to endow with system scalability. Lastly, CPG-based motion generation framework is presented that can generate natural biomimetic motion, and by exploiting the inverse CPG model obtained with machine learning method, it becomes possible to generate certain desired motion while still making CPG generated natural motion.λ³Έ λ
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Όλ¬Έμμλ μ°μ λ§ν¬ λͺ¨λμ λμμΈμ μν΄ μ λ°©ν₯μΌλ‘ 보μ₯λλ νκ³Ό ν ν¬μ ν¬κΈ°λ₯Ό μ΅λννλ ꡬμ μ΅μ νλ₯Ό μ¬μ©νκ³ , μ€μ μ μ©κ°λ₯ν ν΄λ₯Ό μ»κΈ° μν΄ λͺκ°μ§ ꡬμ쑰건(λ‘ν° κ° κ³΅κΈ° νλ¦ κ°μμ ννΌ λ±)μ κ³ λ €νλ€. λν μΌμκ° μλ μ‘μΈμμ΄ν°λ‘ μλ°©ν₯ μΆλ ₯μ λ΄λ κ²μμ μΌκΈ°λλ ESC μ λ° νΉμ΄μ (ESC-induced singularity) μ΄λΌλ λ¬Έμ λ₯Ό μ²μμΌλ‘ μκ°νκ³ , μ΄λ₯Ό ν΄κ²°νκΈ° μν΄ μ νμ 맡ν (selective mapping) μ΄λΌλ κΈ°λ²μ μ μνλ€. μ 체 LASDRA μμ€ν
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μ΄ μνλ μμ§μμ λΌ μ μλλ‘ νλ€.1 Introduction 1
1.1 Motivation and Background 1
1.2 Research Problems and Approach 3
1.3 Preview of Contributions 5
2 Omni-Directional Aerial Robot 7
2.1 Introduction 7
2.2 Mechanical Design 12
2.2.1 Design Description 12
2.2.2 Wrench-Maximizing Design Optimization 13
2.3 System Modeling and Control Design 20
2.3.1 System Modeling 20
2.3.2 Pose Trajectory Tracking Control 22
2.3.3 Hybrid Pose/Wrench Control 22
2.3.4 PSPM-Based Teleoperation 24
2.4 Control Allocation with Selective Mapping 27
2.4.1 Infinity-Norm Minimization 27
2.4.2 ESC-Induced Singularity and Selective Mapping 29
2.5 Experiment 38
2.5.1 System Setup 38
2.5.2 Experiment Results 41
2.6 Conclusion 49
3 Pose and Posture Estimation of an Aerial Skeleton System 51
3.1 Introduction 51
3.2 Preliminary 53
3.3 Pose and Posture Estimation 55
3.3.1 Estimation Algorithm via SCKF 55
3.3.2 Semi-Distributed Version of Algorithm 59
3.4 Simulation 62
3.5 Experiment 65
3.5.1 System Setup 65
3.5.2 Experiment of SCKF-Based Estimation Algorithm 66
3.6 Conclusion 69
4 CPG-Based Motion Generation 71
4.1 Introduction 71
4.2 Description of Entire Framework 75
4.2.1 LASDRA System 75
4.2.2 Snake-Like Robot & Pivotboard 77
4.3 CPG Model 79
4.3.1 LASDRA System 79
4.3.2 Snake-Like Robot 80
4.3.3 Pivotboard 83
4.4 Target Pose Calculation with Expected Physics 84
4.5 Inverse Model Learning 86
4.5.1 LASDRA System 86
4.5.2 Snake-Like Robot 89
4.5.3 Pivotboard 90
4.6 CPG Parameter Adaptation 93
4.7 Simulation 94
4.7.1 LASDRA System 94
4.7.2 Snake-Like Robot & Pivotboard 97
4.8 Conclusion 101
5 Outdoor Flight Experiment of the F-LASDRA System 103
5.1 System Setup 103
5.2 Experiment Results 104
6 Conclusion 111
6.1 Summary 111
6.2 Future Works 112Docto
Topics in Adaptive Optics
Advances in adaptive optics technology and applications move forward at a rapid pace. The basic idea of wavefront compensation in real-time has been around since the mid 1970s. The first widely used application of adaptive optics was for compensating atmospheric turbulence effects in astronomical imaging and laser beam propagation. While some topics have been researched and reported for years, even decades, new applications and advances in the supporting technologies occur almost daily. This book brings together 11 original chapters related to adaptive optics, written by an international group of invited authors. Topics include atmospheric turbulence characterization, astronomy with large telescopes, image post-processing, high power laser distortion compensation, adaptive optics and the human eye, wavefront sensors, and deformable mirrors
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