DGIST Scholar: Development of Advanced Robot Force Control Algorithms

Title

Development of Advanced Robot Force Control Algorithms

Alternative Title

고급 로봇 힘 제어 알고리즘의 개발

DGIST Authors

Kangwagye Samuel ; Sehoon Oh ; Roberto Oboe

Advisor

오세훈

Co-Advisor(s)

Roberto Oboe

Issued Date

2023

Awarded Date

2023-02-01

Citation

Kangwagye Samuel. (2023). Development of Advanced Robot Force Control Algorithms. doi: 10.22677/THESIS.200000652622

Type

Thesis

Description

Robot control

Abstract

In this thesis, advanced model-based robot force control algorithms are developed exploiting the availability of multisensor information towards attenuating the sensor noises and suppressing the effects of force disturbances.
For joint-space single-dof application, a reduced-order multisensor-based force observer (RMFOB) for accurately estimating the force exerted on a load is developed.
To suppress the effects of force disturbances in a robust way, a disturbance observer known as model-based force disturbance observer (FDOB) is proposed.
Then, the RMFOB and FDOB are combined in a closed-loop setting to form a twofold observer-based force control system. Design methodology and systematic parameter tuning criteria for this double observer-based force control is developed. And lastly, towards high-performance motion control and contact stability, a novel integrated DOB (IDOB) is also developed and its effectiveness evaluated.
The IDOB design concept is applied to a multi-dof system where an outer-loop integrated DOB-based admittance control method in task space (OIDOBt) is developed. This is implemented in task-space and outside the inner position/velocity control loop for the 6-DOF industrial manipulator.

더보기 ;

본 논문에서는 다중 센서 정보를 활용한 고급 모델 기반 로봇 힘 제어 알고리즘을 제안한다.
관절 공간에서 단일 자유도를 가지는 어플리케이션에 적용하기 위해, 로봇의 외력 측정 정확도를 높이는 다중센서 기반 축소차원 힘관측기(RMFOB) 알고리즘이 개발된다. 그리고 힘 외란의 영향을 강인한 방식으로 억제하기 위해 모델 기반 힘외란관측기(FDOB)로 알려진 외란관측기가 제안된다.
또한, RMFOB와 FDOB가 폐쇄 루프 설정에서 결합되어 이중 관측기 기반 힘 제어 시스템을 형성한다. 이 이중 관측기 기반 힘 제어 시스템을 (복잡하지 않게) 개발하기 위한 설계 방법론과 체계적인 매개 변수 조정 방법을 제안한다. 마지막으로 고성능 모션 제어와 접촉 시의 안정성을 위해 새로운 통합외란관측기(IDOB)가 개발되고 그 효과 또한 평가된다.
다자유도 시스템을 위해서는, 작업 공간의 외부 루프 통합외란관측기 기반 어드미턴스 제어 방법(OIDOBt)이 개발된다. 이 방법은 6자유도 산업용 로봇를 위한 작업 공간과 내부 위치/속도 제어 루프 바깥에 구현된다.

Table Of Contents

I. Introduction 1
1.1 Research Background 1
1.2 Related Literature 2
1.2.1 Force Measurement and Estimation 2
1.2.2 Force Control 5
1.3 Thesis Contributions 7
1.4 Thesis Flow and Overview 10
1.5 List of Publications 11
1.5.1 Journal Papers 11
1.5.2 Conference Papers 12
II. Force Control Problem Description For a Single-DOF System 14
2.1 Generalized Single-DOF System 14
2.2 Modeling of Force Sensor-Based Force Servo System 14
2.3 System Description Including Noise Characteristic 19
2.4 Disturbances in Force Control System 21
III. A Reduced-Order Multisensor-Based Force Observer 22
3.1 Design and Analysis of the RMFOB 22
3.1.1 State Transformation and State-space Derivation 24
3.1.2 Extraction of Force and Measurement Offsets States 27
3.2 Discussion of the RMFOB Characteristics 29
3.3 Verification of the Proposed RMFOB 30
3.3.1 Experiment Design 31
3.3.2 Validation of Offsets Compensation Using Simulations 33
3.3.3 Experimental Verification 36
3.4 Conclusions on RMFOB Design 42
IV. Twofold Observer-Based Precise Force Control 43
4.1 Proposed Twofold Observer-Based Force Control System 43
4.2 Estimation of Accurate Interaction Forces with RMFOB 43
4.3 Estimation and Suppression of Disturbances with FDOB 44
4.4 Development of Parameter Tuning Criterion 45
4.4.1 Step 1: Derivation of the output equation 46
4.4.2 Step 2: Effect of noises and disturbances on force output 47
4.4.3 Step 3: Quantitative formulation 47
4.5 Analysis of Proposed Force Control System 50
4.5.1 RMFOB and FDOB Performance Analysis 50
4.5.2 Robust Stability Analysis 51
4.5.3 Assessment of Effect of Observer Cutoff Frequency 53
4.6 Simulation and Experiments 54
4.6.1 Experiment Design 54
4.6.2 Simulation Study 55
4.6.3 Experimental Validation 55
4.7 Conclusion on Twofold Observer Control 58
V. Integrated Disturbance Observer-Based Robust Force Control 60
5.1 Introduction 60
5.2 Design and Analysis of Robust Force Control Systems with Force-Based DOBs 62
5.3 Design of Force-Based Disturbance Observers 64
5.3.1 CFDOB and FDOB 64
5.3.2 Integrated Disturbance Observer 65
5.4 Structural, Tracking Performance, and Stability Analyses of Force-DOB-Based Robust Force Control Systems 67
5.5 Contact Stability Analysis 69
5.6 Influence of Force Sensor, Motor Encoder, and Motor Current Noises to Disturbance Estimation Performance 71
5.7 Analysis of Influence of Model Uncertainty 72
5.7.1 Disturbance Suppression Performance Analysis 73
5.7.2 Analysis of Stability Against Model Uncertainty 74
5.8 Experimental Verification 76
5.8.1 Experiment Design 76
5.8.2 Experiments 77
5.9 Conclusions on IDOB Design 86
VI. Application of DOB to Admittance Control of Multi-DOF Industrial Robot 87
6.1 Introduction 87
6.2 Problem Description 89
6.2.1 The Robot and its Basic Admittance Control Method 90
6.3 Limitations of Basic Admittance Control Method 94
6.3.1 Desired Admittance Rendering Limitation 95
6.3.2 Contact Stability Limitation 95
6.3.3 Constraint of Inner-loop Velocity Control 96
6.4 Design of Proposed Control Method 97
6.4.1 Proposed Control Architecture 97
6.4.2 Detailed Design of the DOBs 97
6.5 Closed-Loop Analysis 100
6.5.1 Rendered Admittance Limitation Evaluation 100
6.5.2 Contact Stability Limitation Evaluation 101
6.5.3 Robustness to Payload Mass Variations 103
6.5.4 Disturbance Rejection and Norminalization 104
6.5.5 Influence of Sensor Noises on Disturbance Estimation Performance 105
6.6 Experimental Validation 106
6.6.1 Parameter Determination For Robot and DOB Models 106
6.6.2 Controller Implementation 108
6.6.3 Exp 1: Admittance Rendering in Free Space 109
6.6.4 Exp 2: Contact With Stiff Surface 110
6.6.5 Exp 3: High Speed Force Control 114
6.7 Conclusions on DOB Application for Admittance Control 116
VII. General Conclusion 119
7.1 Conclusion 119
7.2 Future Works 120
References 122

URI

http://hdl.handle.net/20.500.11750/45778
http://dgist.dcollection.net/common/orgView/200000652622

DOI

10.22677/THESIS.200000652622

Degree

Doctor

Department

Department of Robotics and Mechatronics Engineering

Publisher

DGIST

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