PRECISION MOTION AND ENERGY EXCHANGE CONTROL ON ROBOT’S LEG

INTERACTION WITH SOFT SURFACE

WAN MOHD NAFIS BIN WAN LEZAINI

Master of Science

UNIVERSITI MALAYSIA PAHANG

SUPERVISOR’S DECLARATION

We hereby declare that we have checked this thesis and in our opinion, this thesis is

adequate in terms of scope and quality for the award of the degree of Master of Science.

_______________________________

(Supervisor’s Signature)

Full Name : IR. DR. ADDIE IRAWAN BIN HASHIM

Position : SENIOR LECTURER

Date :

_______________________________

(Co-supervisor’s Signature)

Full Name : DR. AHMAD NOR KASRUDDIN BIN NASIR

Position : SENIOR LECTURER

Date :

4/4/2019

3/4/2019

STUDENT’S DECLARATION

I hereby declare that the work in this thesis is based on my original work except for

quotations and citations which have been duly acknowledged. I also declare that it has not

been previously or concurrently submitted for any other degree at Universiti Malaysia

Pahang or any other institutions.

_______________________________

(Student’s Signature)

Full Name : WAN MOHD NAFIS BIN WAN LEZAINI

ID Number : MEL16016

Date : 3/4/2019

3

PRECISION MOTION AND ENERGY EXCHANGE CONTROL ON ROBOT’S LEG INTERACTION WITH SOFT SURFACE

WAN MOHD NAFIS BIN WAN LEZAINI

Thesis submitted in fulfillment of the requirements for the award of the degree of

Master of Science

Faculty of Electrical & Electronics Engineering

UNIVERSITI MALAYSIA PAHANG

MARCH 2019

ii

ACKNOWLEDGEMENTS

In the name of Allah, the Most Beneficent and the Most Merciful.

First and for most, I am really thankful to Allah the Almighty, and the Merciful for providing me the strength and the idea to finish this research. My greatest and deepest thankfulness to my supervisor, Ir. Dr Addie Irawan bin Hashim, for accepting and allowing me for this wonderful experience and yet interesting master project. His supervision and dedication, both helped me to channel ideas and at the same time provided a good freedom in exploring new things. I am very grateful for his endless encouragement for me to complete my master study and he also willing to share his own experiences, ideas and devote his free time to supervise me in the implementation and finishing this project.

My great indebtedness and thankful also goes to my mother who deeply immense in difficulties just to educate her children up until higher level in education. Her affection and love always brought happiness to my life. Her non-stop encouragement motivates me in continuing this task until the end.

Last but not least, my great gratitude also dedicated to my friends and those whom involve directly or indirectly during finishing this master study. Finally, I really hope that all the knowledges, ideas and experiences that I gained through this project can be shared and provide benefits to all.

Thank you.

WAN MOHD NAFIS BIN WAN LEZAINI

iii

ABSTRAK

Pelbagai idea telah dibentangkan dalam membangunkan rekabentuk robot berasaskan rupa biologi makhluk hidupan sebenar seperti robot berkaki, robot terbang, robot berenang dan lain-lain. Dalam pembangunan sistem kawalan dan mekanisma rekabentuk robot berkaki, faktor keseluruhan kestabilan sistem mestilah diambil kira dan bukan sahaja faktor manipulasi dibahagian kakinya. Walau bagaimanapun kestabilan manipulasi sistem kaki robot ini tetap menjadi menjadi keutamaan dan asas untuk menjamin kestabilan sistem keseluruhan robot. Salah satu cabaran dalam kawalan manipulasi pada setiap kaki robot berkaki adalah untuk mengekalkan ketepatan gerakan sudut setiap sendi kakinya. Keperluan sistem kawalan yang mantap menjadi lebih tinggi dengan peningkatan bilangan darjah kebebasan setiap kaki robot dimana penyelarasan yang tepat diperlukan dalam ruang kerja kaki tersebut. Selain itu, faktor tidak linear dalam gerakan kaki robot juga perlu ditangani untuk memastikan kestabilan dinamik keseluruhan robot berkaki terutama ketika berjalan di kawasan yang tidak rata. Kaedah yang popular seperti kawalan impedans telah digunakan secara meluas dengan memahami interaksi dinamik diantara tapak kaki robot dan permukaan persekitaran yang hendak dipijak. Kebanyakan usaha penyelidikan telah tertumpu kepada kawalan dinamik yang dapat menempatkan semula kedudukan kaki robot semasa berjalan dikawasan berpermukaan yang tidak rata dan keras. Kaedah ini mungkin tidak sesuai untuk permukaan lembut yang memerlukan kaki robot untuk menahan medium sambil menolak badannya walaupun penyesuaian pada ketegangan permukaan telah dilakukan. Akibatnya, robot berkemungkinan besar akan terbalik atau terjatuh kerana kaki robot akan tergelincir berfaktorkan daripada tenaga yang rendah yang digunakan oleh setiap kaki robot tersebut. Oleh itu, di sini terdapat dua kenyataan masalah yang dapat diklasifikasikan iaitu implikasi pada ketidaktepatan gerakan sendi kaki dan pertukaran tenaga tak terkawal dalam gerakan dinamik kaki robot tersebut. Oleh itu, kajian tesis ini telah mengambil inisiatif untuk mencadangkan dua penyelesaian untuk isu-isu yang disebutkan di atas iaitu sistem kawalan Propotional Integral-Antiwindup-Fuzzy Logic-Derivative (PIA-FLC-D) untuk ketepatan gerakan setiap sendi kaki robot dan kawalan impedans untuk kestabilan dinamik kaki robot. PIA-FLC-D dicadangkan untuk mengatasi ketepatan bersama kaki yang terjejas oleh faktor graviti yang tidak linear. Kawalan impedans dikira dan diperolehi untuk memenuhi pembentukan halaju yang sesuai secara tidak langsung kepada pertukaran tenaga kaki yang dikhususkan pada setiap heretan kaki robot. Dalam kajian ini Hexapod-to-Quadruped (Hexaquad) robot digunakan sebagai sistem sasaran dalam mengesahkan teori-teori sistem kawalan yang dicadangkan. Merujuk kepada beberapa eksperimen yang telah dibuat, cadangan sistem kawalan PIA-FLC-D yang telah menunjukkan keputusan yang sangat baik dengan kelewatan masa hanya 0.1 saat berbanding sistem kawalan sebelumnya yang mengalami kelewatan masa 0.25 saat ketika kawalan ketetapan kaki. Bagi kes eksperimen terhadap cadangan kawalan impedans, keputusan menunjukkan bahawa kelajuan pergerakan kaki Hexaquad robot meningkat dengan daya yang dikenakan pada kedudukan menegak dan secara tidak langsung menyebabkan tenaga meningkat pada kaki tanpa mengubah bentuk asal pergerakan kaki robot tersebut. Dengan menggunakan kaki Hexaquad robot yang sama, ianya diuji diatas permukaan lembut (pasir) dan dalam pada masa yang sama, menanggung berat badan robot. Hasil keputusan menunjukkan ketika fasa mengheret, dengan mengunakan cadangan kawalan impedans, setiap sendi pada kaki tersebut mampu mengikut gerakan rujukan dengan tepat berbanding jika tidak menggunakannya.

iv

ABSTRACT

Nowadays, various ideas have been presented in developing bio-inspired robot such as legged, flying, swimming and other crawling mechanisms. Generally legged robot development and control covered beyond manipulation issues in which stability of the overall system need to be catered as well. Stable leg manipulation for a legged robot becomes a priority to guarantee the whole system stability. One of the challenges in legged robot manipulation control is to sustain the leg’s joint angular motion precision. As the number of degrees of freedom for a leg is increased, the demand for robust control becomes higher since it requires precise coordination in foot workspace. Besides that, the nonlinearity factor in robot’s leg motion also need to be tackled to ensure the overall stability of a legged robot especially during walking on uneven terrain. Popular method such as impedance control has been extensively used by understanding dynamic interaction between leg tips and the environment. Most of the researched had emphasized on dynamic control that is able to reposition robot’s foot placement during walking on the unstructured terrain with hard surfaces. This method may not be suitable for soft surface that required robot’s leg to withstand the ground medium while pushing its body although repositioning was done. As a result, the overturning may happen to the robot since the robot’s foot will slip due to the low energy to adapt with environment surface stiffness. Here, there are two problem statements which are implication of imprecision of leg joint motion and uncontrollable energy exchange in foot dynamic motion. Therefore, this study has taken initiative to propose two solutions for the aforementioned issues which are hybrid Proportional Integral-Antiwindup-Fuzzy Logic Control-Derivative (PIA-FLC-D) and impedance control respectively. PIA-FLC-D is proposed to overcome leg’s joint precision affected by nonlinear gravitational factor. On the other hand, impedance control is derived to cater the velocity shaping as indirectly controlling the energy exchange of the leg specifically at leg dragging period. A bio-inspired robot named Hexapod-to-Quadruped (Hexaquad) robot is used as the targeted platform for verification and validation. The proposed PIA-FLC-D was verified and the results were compared with the predecessor controllers. The results show that PIA-FLC-D performs fast response with only 0.1s delay compared to its predecessor controller with 0.25s delay during trajectory tracking. For the case of the impedance control, the results show that Hexaquad’s leg velocity increases with the contact force on vertical position in which resulting energy increased on the leg while maintaining the overall leg motion shape. The same Hexaquad’s leg that applied the proposed impedance controller also tested completing the walking motion on the soft surface medium (dry sand) while bearing the robot’s body weight. The results showed that during drag sequence, by using the proposed controller, each joint of Hexaquad’s leg manage to follow the reference motion precisely compared to without using the proposed controller.

v

TABLE OF CONTENT

DECLARATION

TITLE PAGE

ACKNOWLEDGEMENTS ii

ABSTRAK iii

ABSTRACT iv

TABLE OF CONTENT v

LIST OF TABLES viii

LIST OF FIGURES ix

LIST OF SYMBOLS xii

LIST OF ABBREVIATIONS xiv

CHAPTER 1 INTRODUCTION 1

1.1 Research Background 1

1.2 Problem Statements 3

1.3 Objectives 6

1.4 Scopes 6

1.5 Roadmap of the Thesis 7

CHAPTER 2 LITERATURE REVIEW 9

2.1 Introduction 9

2.2 Review on Legged Robot System Research and Development 10

2.2.1 Legged Robot and Its Stability 11

2.2.2 Leg Configuration 14

2.2.3 General Issues in Multi-Legged Robot 15

2.3 Position Control in Legged Robot System 17

2.4 Dynamic Control and Force Interaction in Multi-limbed System 19

vi

2.5 Summary 22

CHAPTER 3 METHODOLOGY 24

3.1 Introduction 24

3.2 Overview on Configurable Hexapod to Quadruped (Hexaquad) Robot 25

3.3 General Control Structure for Hexaquad Robot Leg 29

3.3.1 A Hexaquad Leg Motion Trajectory 30

3.3.2 A Hexaquad Leg Kinematics 33

3.4 Position Control for n-joint Positioning of Hexaquad’s Leg 34

3.4.1 Modification on n-joint Position Control by Addition of

Derivative Element 37

3.5 Dynamic Control for A Hexaquad’s Leg Energy Exchange Control 38

3.5.1 Dynamic Model for A Hexaquad’s Leg: Jacobian Matrix 38

3.5.2 Dynamic Model of Hexaquad’s Leg: Euler-Lagrange Method 41

3.5.3 Impedance Control for Dynamic Variable Speed in Leg

Dragging Motion 46

CHAPTER 4 RESULTS AND DISCUSSION 49

4.1 Introduction 49

4.2 Experimental and Result Performances of PIA, FLC and Combination

of PIA-FLC Control on an n-joint of Hexaquad Leg 49

4.2.1 Modification on the Proposed PIA-FLC Control and Result

Performances on n-joint of Hexaquad Leg 54

4.3 Simulations, Experimental and Result Performances on Proposed Leg

Speed Variation using Impedance Control 56

4.3.1 Verification and Result Performances on Proposed Leg Speed

Variation using Impedance Control System 57

4.3.2 Validations on Proposed Dynamic Leg Speed Variation for

the Case of without Robot’s Body Weight Impact Consideration 59

vii

4.3.3 Validations on Proposed Dynamic Leg Speed Variation for

the Case of with Robot’s Body Weight Impact Consideration 65

CHAPTER 5 CONCLUSION 70

5.1 Conclusion 70

5.2 Recommendation 71

REFERENCES 72

PUBLICATIONS BY AUTHOR 77

APPENDIX A Detail steps of forward Kinematic Calculation for Hexaquad

Leg 78

APPENDIX B Generated force on z-axis 81

viii

LIST OF TABLES

Table 3.1 Actuator Specification Configured for Hexaquad Robot 28

Table 3.2 Rule Base for FLC 37

Table 4.1 FLC Constant Outputs For 𝜃𝜃2 and 𝜃𝜃3 51

Table 4.2 Gain Parameters for PIA and PIA-FLC 53

ix

LIST OF FIGURES

Figure 1.1 Example of multi-legged robot foot motion and leg orientation

during locomotion 4

Figure 1.2 Example of a hexapod robot walking in mudflat (soft terrain)

while four of its legs sink in the medium 5

Figure 1.3 Example of the legged robot with manipulation tasks and

remain moving legs experience weight variation scenarios while

holding the picked payload. 6

Figure 2.1 Mark by yellow, black circle (a) COM (b) COP (c) COG 11

Figure 2.2 The different of POS between different legged robots

(a) Bipedal robot, (b) Hexapod robot 13

Figure 2.3 Example of COG position between (a) Hexapod and (b)

Quadruped robots leg sequences during walking period 13

Figure 2.4 Example of legged robots and its stability criteria 14

Figure 2.5 Typical robot’s leg design (a) Sprawling-type leg, (b)

Mammal-type leg 15

Figure 2.6 Division of research and development sections in legged robot

system 16

Figure 2.7 Basic impedance model structure 21

Figure 3.1 Overview of Hexaquad robot system 26

Figure 3.2 Leg orientation and configuration of Hexaquad robot from

biological crab structure 27

Figure 3.3 Driven module diagram for a leg of Hexaquad robot 27

Figure 3.4 Hexaquad’s leg with novel actuating frame concept

(a) Solid model overall leg (b) Motion diagram 28

Figure 3.5 Overview on proposed control architecture for a leg of

Hexaquad robot in facing soft terrain 30

Figure 3.6 Semi-circle pattern on Simulink graph plotter 31

Figure 3.7 Link orientation of a Hexaquad’s leg 33

Figure 3.8 Detail diagram of proposed PIA-FLC scheme for n-joint leg of

Hexaquad robot position control 37

Figure 3.9 Overall position control structure of n-joint leg of Hexaquad

robot 37

x

Figure 3.10 A modified version of PIA-FLC-D joint position control 38

Figure 3.11 Legged robot walking on the muddy type medium 47

Figure 3.12 Proposed impedance control to alter velocity during drag phase 48

Figure 4.1 Experimental setup for joint position control of the second leg

of Hexaquad 51

Figure 4.2 Membership functions (MF) design using the triangular shape

for PIA-FLC 52

Figure 4.3 Graphical relationship between input and output MF of

PIA-FLC; (a) 2θ , (b) 3θ 52

Figure 4.4 Sample experimental results of2θ with FLC, PIA and proposed

PIA-FLC system; (a) 3.1s to 4.8s, (b) 4.6s to 5.6s 54

Figure 4.5 Sample experimental results of 3θ for FLC, PIA and proposed

PIA-FLC system; (a) 3.2s to 5.0s, (b) 5.0ss to 5.6s 54

Figure 4.6 Sample experiment of 2θ 55

Figure 4.7 Sample experiment of 3θ 56

Figure 4.8 Forward Kinematic verification of y-axis 56

Figure 4.9 Forward Kinematic verification of z-axis 57

Figure 4.10 Force generated from simulation (rzF and

fzF ) 59

Figure 4.11 Error Force ( fe ) 59

Figure 4.12 Impedance behavior for a full cycle leg motion 60

Figure 4.13 Control architecture of Hexaquad’s leg after excluding dynamic

models 61

Figure 4.14 Test rig setup on the first leg of Hexaquad 61

Figure 4.15 Height of chair is adjusted to regulate extF to obtain

approximately (a) 0N (b) 40N (c) 80N (d) 100N 62

Figure 4.16 Sample from experimental result (a) external force, extF (b) s

from impedance control 63

Figure 4.17 Sample from experimental results (a) velocity on 2θ (b) total

kinetic energy, kE on Hexaquad’s leg 65

xi

Figure 4.18 Sample experimental results (a) Y-axis reference tracks (b)

Z-axis reference tracks (c) Y-axis feedback tracks (d)

Z-axis feedback tracks 66

Figure 4.19 Experiment setup For Case with Robot’s Body Weight

Impact 67

Figure 4.20 Sample from experimental results for both joints

(Original motion) 68

Figure 4.21 Sample from experimental results for both joints

(without impedance) 69

Figure 4.22 External force acting on the leg during drag phase without

using impedance control 69

Figure 4.23 Sample from experimental results for both joints

(with impedance) 70

Figure 4.24 External force acting on the leg during drag phase with using

impedance control 70

xii

LIST OF SYMBOLS

TW Total Weight

RW Robot Weight

pW Payload Weight

u(t) Control Output

nθ n-Joint

nfθ n-Joint Feedback

θ Joint Velocity

θ Joint Acceleration

fθ Feedback Joint Velocity

fθ Feedback Joint Acceleration

extF External Force

fzF

Feedback Force on z-axis

rzF Force Reference on z-axis

RF Force Reference

fe Force Error

s∆ Position state

s∆ Velocity State

s∆ Acceleration state

dragT Drag Period

swingT Swing Period

swingV Swing Velocity

dragV Drag Velocity

TT One Full Cycle

os Width of pattern

oh Height of pattern

xiii

kd Actuator length

na n-link length

nτ n-joint Torque

( )oxyz Initial starting point of walking motion

( )oOXYZ Origin on Cartesian

neθ Angular joint error

( )ntδ PI-antiwindup controller output

( )nu t current control output

( 1)nu t − previous value of control output

sT sampling time gain

IK proportional gain

PK integral gain

TK antiwindup gain

nvJ Jacobian for link linear velocity

nJω Jacobian for link rotational velocity

KE Kinetic Energy

PE Potential Energy

compI Inertia component

( )G θ Gravity vector

ζ Damping ratio

swingT∆ Swing motion rate of change

dragT∆ Drag motion rate of change

xiv

LIST OF ABBREVIATIONS

2D Two Dimensional

COG Centre of Gravity

COM Centre of Mass

COP Centre of Pressure

DOF Degree of Freedom

FLC Fuzzy Logic Control

FTG

MFC

Foot to Gripper

Model Following Control

NN Neural Network

PI Proportional Integral

PIA Proportional Integral Antiwindup

PID Proportional Integral Derivative

PIA-FLC Proportional Integral Antiwindup-Fuzzy Logic Control

PIA-FLC-D Proportional Integral Antiwindup-Fuzzy Logic Control-Derivative

POS Polygon of Support

SEA Series of elastic actuator

SISO Single Input Single Output

UGV Unmanned Ground Vehicle

72

REFERENCES

Adewuyi, P. A. (2013). Dc motor speed control: A case between pid controller and fuzzy logic controller. international journal of multidisciplinary sciences and engineering, 4(4), 36-40.

Altendorfer, R., Koditschek, D. E., & P. Holmes. (2004). Stability Analysis of a Clock-Driven Rigid SLIP Model for RHex. International Journal of Robotics Research, 23(10).

Ayas, M. S., & Altas, I. H. (2017). Fuzzy logic based adaptive admittance control of a redundantly actuated ankle rehabilitation robot. Control Engineering Practice, 59, 44-54. doi: http://dx.doi.org/10.1016/j.conengprac.2016.11.015

Bartholet, T. (1985). Robot applications for nuclear power plant maintenance: Odetics, Inc., Anaheim, CA (USA).

Batts, Z., Kim, J., & Yamane, K. (2016). Untethered one-legged hopping in 3d using linear elastic actuator in parallel (leap). Paper presented at the International Symposium on Experimental Robotics.

Bekey, G. A. (2005). Autonomous robots: from biological inspiration to implementation and control: MIT press.

Bjelonic, M., Kottege, N., & Beckerle, P. (2016, 9-14 Oct. 2016). Proprioceptive control of an over-actuated hexapod robot in unstructured terrain. Paper presented at the 2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS).

Boaventura, T., Buchli, J., Semini, C., & Caldwell, D. G. (2015). Model-Based Hydraulic Impedance Control for Dynamic Robots. IEEE Transactions on Robotics, 31(6), 1324-1336. doi: 10.1109/TRO.2015.2482061

Boisclair, J., Richard, P. L., Laliberté, T., & Gosselin, C. (2017). Gravity Compensation of Robotic Manipulators Using Cylindrical Halbach Arrays. IEEE/ASME Transactions on Mechatronics, 22(1), 457-464. doi: 10.1109/TMECH.2016.2614386

Centre of Mass & Centre of Pressure: So Close, Yet So Far. (2014). from https://www.youtube.com/watch?v=JY-ipk-EN4U

Cigola, M., Ceccarelli, M., & Carbone, G. (2005). Application of robots for inspection and restoration of historical sites.

Eich, M., Grimminger, F., & Kirchner, F. (2008). A versatile stair-climbing robot for search and rescue applications. Paper presented at the Safety, Security and Rescue Robotics, 2008.

Erickson, D., Weber, M., & Sharf, I. (2003). Contact Stiffness and Damping Estimation for Robotic Systems. International Journal of Robotics Research, 22(1).

Fukuoka, Y., Kimura, H., & Cohen, A. H. (2003). Adaptive Dynamic Walking of a Quadruped Robot on Irregular Terrain Based on Biological Concepts. The International Journal of Robotics Research, 22(3-4), 187-202. doi: 10.1177/0278364903022003004

Galvez, J. A., Estremera, J., & Gonzales de Santos, P. (2003). A new legged-robot configuration for research in force distribution. Mechatronics, 13, 907-932

73

Gassmann, B., Scholl, K. U., & Berns, K. (2001). Locomotion of LAURON III in rough terrain. Paper presented at the Proceeding of IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2001 Como, Italy.

Guo, S., Guo, J., Wang, P., Wei, W., Ji, Y., & Wang, Y. (2013, 4-7 Aug. 2013). A novel master-slave robotic catheter system for Vascular Interventional Surgery. Paper presented at the Mechatronics and Automation (ICMA), 2013 IEEE International Conference.

Hasan, A. T. (2012). Under-Actuated Robot Manipulator Positioning Control Using Artificial Neural Network Inversion Technique. Advances in Artificial Intelligence, 2012, 6. doi: 10.1155/2012/927905

Hogan, N. (1984). Impedance control: An approach to manipulation. Paper presented at the American Control Conference, 1984.

Hogan, N. (1987). Stable execution of contact tasks using impedance control. Paper presented at the Proceeding of IEEE International Conference on Robotics and Automation 1987, Raleigh, North Carolina.

Hutter, M., Gehring, C., Hopflinger, M. A., Blosch, M., & Siegwart, R. (2014). Toward combining speed, efficiency, versatility, and robustness in an autonomous quadruped. Robotics, IEEE Transactions on, 30. doi: 10.1109/tro.2014.2360493

Irawan, A., Jiun, H. L., & Alam, M. M. (2014). Control input converter for robot's leg joint with parallel actuation configuration. Paper presented at the Electrical and Computer Engineering (ICECE), 2014 International Conference.

Irawan, A., Nonami, K., & Daud, M. R. (2013). Optimal Impedance Control with TSK-Type FLC for Hard Shaking Reduction on Hydraulically Driven Hexapod Robot Autonomous Control Systems and Vehicles (pp. 223-236): Springer Japan.

Irawan, A., Razali, A. R., Wan Ishak, W. F., Arshad, M. R., & Yin, T. Y. (2015). Development of hexaquad robot: Modeling and framework. ARPN Journal of Engineering and Applied Sciences, 10(23), 17506-17513.

Irawan, A., Tan, Y. Y., Lezaini, W. M. N. W., Razali, A. R., & Yusof, M. S. M. (2016, 13-14 Dec. 2016). Reconfigurable foot-to-gripper leg for underwater bottom operator, Hexaquad. Paper presented at the 2016 IEEE International Conference on Underwater System Technology: Theory and Applications (USYS).

Jun, B. H., Shim, H., Kim, B., Park, J.-Y., Baek, H., Yoo, S., & Lee, P. M. (2013). Development of seabed walking robot CR200. Paper presented at the OCEANS-Bergen, 2013 MTS/IEEE.

Junqing, C., Xuzhi, L., & Min, W. (2015). Position control method for a planar Acrobot based on fuzzy control. Paper presented at the 2015 34th Chinese Control Conference (CCC).

Kitano, S., Hirose, S., Horigome, A., & Endo, G. (2016). TITAN-XIII: sprawling-type quadruped robot with ability of fast and energy-efficient walking. ROBOMECH Journal, 3(1), 8. doi: 10.1186/s40648-016-0047-1

Komati, B., Clevy, C., & Lutz, P. (2014). Force tracking impedance control with unknown environment at the microscale. Paper presented at the Robotics and Automation (ICRA), 2014 IEEE International Conference.

74

Komati, B., Pac, M. R., Ranatunga, I., Clévy, C., Popa, D. O., & Lutz, P. (2013). Explicit force control vs impedance control for micromanipulation. Paper presented at the ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference.

Li, Y., Wang, G., Dong, B., & Zhao, B. (2015). Hybrid position–force control for constrained reconfigurable manipulators based on adaptive neural network. Advances in Mechanical Engineering, 7(9), 1687814015602409. doi: doi:10.1177/1687814015602409

Lim, H., Setiawan, S. A., & Takanishi, A. (2001). Balance and impedance control for biped humanoid robot locomotion. Paper presented at the Proceeding of IEEE/RSJ International Conference on Intelligent Robots and Systems 2001, Maui, HI , USA.

Luo, B. Y., Li, M. C., Wang, P., & Yu, T. Y. (2015). An Anti-windup Algorithm for PID Controller of PMSM SVPWM Speed Control System. Paper presented at the Proceedings of the 3rd International Conference on Mechatronics, Robotics and Automation (Icmra 2015).

Mallapragada, V., Erol, D., & Sarkar, N. (2007). A New Method of Force Control for Unknown Environments. International Journal of Advanced Robotic Systems, IntechOpen., 4(3).

Nonami, K., Barai, R. K., Irawan, A., & Daud, M. R. (2014). Hydraulically Actuated Hexapod Robots: Design, Implementation and Control: Springer Netherlands.

Ott, C., Mukherjee, R., & Nakamura, Y. (2010). Unified impedance and admittance control. Paper presented at the Robotics and Automation (ICRA), 2010 IEEE International Conference.

Ozawa, R., Kobayashi, H., & Ishibashi, R. (2015). Adaptive impedance control of a variable stiffness actuator. Advanced Robotics, 29(4), 273-286. doi: 10.1080/01691864.2014.985612

Park, J. Y., Shim, H., Jun, B. H., Lee, P. M., Yoo, S. Y., & Baek, H. (2017). Measurement of hydrodynamic forces and moment acting on Crabster, CR200 using model tests. Paper presented at the 2017 IEEE Underwater Technology (UT).

Park., J. H. (2002). Impedance control for biped robot locomotion. IEEE Transactions, Robotics and Automation, 17(6).

Preumont, A., Alexandre, P., Doroftei, I., & Goffin, F. (1997). A conceptual walking vehicle for planetary exploration. Mechatronics, 7(3), 287-296.

Raibert, M., Blankespoor, K., Nelson, G., & Playter, R. (2008). Bigdog, the rough-terrain quadruped robot. IFAC Proceedings Volumes, 41(2), 10822-10825.

Raibert, M. H. (1986). Legged robots that balance: MIT press.

Reher, J., Cousineau, E. A., Hereid, A., Hubicki, C. M., & Ames, A. D. (2016). Realizing dynamic and efficient bipedal locomotion on the humanoid robot DURUS. Paper presented at the Robotics and Automation (ICRA), 2016 IEEE International Conference.

Resceanu, C. F. (2011). Control algorithms for multi-legged robots in fault conditions using fuzzy logic. Paper presented at the 15th International Conference on System Theory, Control and Computing.

Sadun, A. S., Jalani, J., & Sukor, J. A. (2016). An overview of active compliance control for a robotic hand (Vol. 11).

75

Schneider, A., U.Schmucker. (2006). Force Sensing for Multi-Legged Walking Robots: Theory and Experiments Part 2: Force Control of Legged Vehicles Mobile Robotics, Moving Intelligence, IntechOpen.

Semini, C., Tsagarakis, N. G., Guglielmino, E., Focchi, M., Cannella, F., & Caldwell, D. G. (2011). Design of HyQ–a hydraulically and electrically actuated quadruped robot. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 225(6), 831-849.

Seok, S., Wang, A., Chuah, M. Y., Hyun, D. J., Lee, J., Otten, D. M., & Kim, S. (2015). Design Principles for Energy-Efficient Legged Locomotion and Implementation on the MIT Cheetah Robot. IEEE/ASME Transactions on Mechatronics, 20(3), 1117-1129. doi: 10.1109/TMECH.2014.2339013

Siegwart, R., Nourbakhsh, I. R., & Scaramuzza, D. (2011). Introduction to autonomous mobile robots: MIT press.

Song, S. M., & Waldron, K. J. (1989). Machines that Walk: The Adaptive Suspension Vehicle: MIT Press.

Sun, L., Yin, W., Wang, M., & Liu, J. (2018). Position Control for Flexible Joint Robot Based on Online Gravity Compensation With Vibration Suppression. IEEE Transactions on Industrial Electronics, 65(6), 4840-4848. doi: 10.1109/TIE.2017.2772157

Takagi, T., & Sugeno, M. (1985). Fuzzy identification of systems and its applications to modeling and control. IEEE Transactions on Systems, Man, and Cybernetics, SMC-15(1), 116-132. doi: 10.1109/TSMC.1985.6313399

Terashima, K., T.Miyoshi,K.Mouri, H.Kitagawa, P.Minyong. (2009). Hybrid Impedance Control of Massage Considering Dynamic Interaction of Human and Robot Collaboration Systems. Journal of Robotics and Mechatronics, 21(1).

Uemura, M., Kanaoka, K., & Kawamura, S. (2006). Power Assist System for Sinusoidal Motion by Passive Element and Impedance Control. Paper presented at the Proceeding of IEEE International Conference on Robotics and Automation 2006 (ICRA 2006), Orlando, Florida, USA.

Uemura, M., Kanaoka, K., & Kawamura, S. (2007). A New Control Method Utilizing Stiffness Adjustment of Mechanical Elastic Elements for Serial Link Systems. Paper presented at the Proceeding of IEEE International Conference on Robotics and Automation 2007 (ICRA 2007), Roma, Italy.

Uemura, M., & Kawamura, S. (2009). Resonance-based Motion Control Method for Multi-Joint Robot through Combining Stiffness Adaptation and Iterative Learning Control. Paper presented at the Proceeding of IEEE International Conference on Robotics and Automation 2009 (ICRA 2009), Kobe, Japan.

Wang., X., Y.Cui. (2010). Self-tuning Fuzzy Compensation based Adaptive Impedance Control for Robotic Machining. Paper presented at the Proceeding of 2nd International Conference on Computer Engineering and Technology (ICCET), Chengdu, China.

Winck, R. C., Elton, M., & Book, W. J. (2015). A practical interface for coordinated position control of an excavator arm. Automation in Construction, 51, 46-58. doi: http://dx.doi.org/10.1016/j.autcon.2014.12.012

76

Zainol, M. A. F. (2016). Precision Control on Hexaquad Robot's Leg Using Anti-windup PID Control Approach. Universiti Malaysia Pahang.

Zou, W., Yang, Z., Tan, W., Wang, M., Liu, J., & Yu, N. (2016). Impedance control of a cable-driven series elastic actuator with the 2-DOF control structure. Paper presented at the 2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS).