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Isaksson, Magnus
Publications (10 of 69) Show all publications
Masud, N., Rafique, S., Smith, C. & Isaksson, M. (2023). Design control and actuator selection of a lower body assistive exoskeleton with 3-D passive compliant supports. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 45(12), Article ID 611.
Open this publication in new window or tab >>Design control and actuator selection of a lower body assistive exoskeleton with 3-D passive compliant supports
2023 (English)In: Journal of the Brazilian Society of Mechanical Sciences and Engineering, ISSN 1678-5878, E-ISSN 1806-3691, Vol. 45, no 12, article id 611Article in journal (Refereed) Published
Abstract [en]

Physical human–robotic interaction is a crucial area of concern for robotic exoskeletons. Lower weight requirement for the worn exoskeletons limits the number and size of joint actuators, resulting in a low active degree of freedom for the exoskeletons with joint actuators having limited power and bandwidth. This limitation invariably results in reduced physical human–robotic interaction performance for the exoskeleton. Recently several techniques have been proposed for the low active degree of freedom exoskeletons with improved physical human–robotic interaction performance using better load torque compensators and improved active compliance. However, effective practical implementation of these techniques requires special hardware and software design considerations. A detailed design of a new lower body exoskeleton is proposed in this paper that can apply these recently developed techniques to practically improve the physical human–robotic interaction performance of the worn exoskeletons. The design presented includes the exoskeleton's structural design, new joint assemblies and the design of novel 3-D passive, compliant supports. A methodology of selecting and verifying the joint actuators and estimating the desired assistive forces at the contact supports based on human user joint torque requirements and the degree of assistance is also thoroughly presented. A new CAN-based master–slave control architecture that supports the implementation of recent techniques for improved physical human–robotic interaction is also fully presented. A new control strategy capable of imparting simultaneous impedance-based force tracking control of the exoskeleton in task space using DOB-based-DLTC at joint space is also thoroughly presented. Simulation verification of the proposed strategy based on the actual gait data of elderly is presented lastly.

Place, publisher, year, edition, pages
Springer, 2023
Keywords
Design; Exoskeleton; Lower body; Master–slave control; Physical human–robotic interaction
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-43249 (URN)10.1007/s40430-023-04480-8 (DOI)001093313100001 ()2-s2.0-85175719993 (Scopus ID)
Available from: 2023-11-13 Created: 2023-11-13 Last updated: 2023-11-23Bibliographically approved
Rafique, S., Rana, S. M., Björsell, N. & Isaksson, M. (2023). Using robotic exoskeletons to reduce muscle activity of workers. In: : . Paper presented at International Conference on Advances in Robotics, AIR 2023, Ropar, 5-8 July 2023. ACM
Open this publication in new window or tab >>Using robotic exoskeletons to reduce muscle activity of workers
2023 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents an experimental study demonstrating the advantages of different exoskeletons while performing workers' tasks. The study illustrates that how the use of certain upper and lower body exoskeletons can reduce the muscle effort around the shoulder, hip, and knee joints. Therefore, overhead, shoulder level, virtual chair position, and deep squatting position drilling tasks were performed, and muscle activity was recorded using EMG sensors. The muscle activity of the participants was compared with and without wearing exoskeletons while performing the same tasks. It was found that up to 60% reduction in the human effort can be achieved while performing the same tasks using exoskeletons. Many of the large-scale automobile manufacturers have already adopted exoskeletons in their assembly lines, however, the use of exoskeletons in small and medium enterprises (SMEs) is still not recognized. Therefore, this study aims to create awareness and accelerate adoption of exoskeletons among SMEs and construction workers.

Place, publisher, year, edition, pages
ACM, 2023
Series
ACM International Conference Proceeding Series
Keywords
assistance for workers; EMG sensor; evaluation of exoskeletons; muscle activity; musculoskeletal disorders
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-43496 (URN)10.1145/3610419.3610473 (DOI)2-s2.0-85179891374 (Scopus ID)9781450399807 (ISBN)
Conference
International Conference on Advances in Robotics, AIR 2023, Ropar, 5-8 July 2023
Available from: 2023-12-25 Created: 2023-12-25 Last updated: 2023-12-25Bibliographically approved
Jain, P., Bera, T. K., Singla, A. & Isaksson, M. (2022). Linear actuator–based knee exoskeleton for stand–sit–stand motions: a bond graph approach. Simulation (San Diego, Calif.), 98(8), 627-644
Open this publication in new window or tab >>Linear actuator–based knee exoskeleton for stand–sit–stand motions: a bond graph approach
2022 (English)In: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 98, no 8, p. 627-644Article in journal (Refereed) Published
Abstract [en]

People with knee disorders often find it difficult to perform common mobility tasks, such as stand–sit–stand motions. High knee torque is required to complete such transitions, as the chances of toppling increase during these motions. Most of the existing conventional approaches, such as wheelchairs and crutches, have failed to provide complete independence to the users. Conversely, contemporary systems like lower body exoskeletons which are bulky, complex, and expensive do not specifically target the knee joint instead of assisting other joints. Hence, there is a need to aid the knee joint using a robotic knee exoskeleton capable of accurately providing the desired knee torque. In the present work, to assist the user in performing the stand–sit–stand motions, an electromyography sensor-based four-bar knee exoskeleton actuated by a linear actuator is proposed. The modeling of the complete exoskeleton is developed using bond graph technique, as the components exist in different energy domains and it is possible to frame a dynamic bond graph model using only kinematic equations. The prototype is fabricated, and experiments are carried out on an artificial limb to prove the efficacy of the design of the current knee exoskeleton. The assistive torque developed by the actuator at the knee joint of the exoskeleton is found to be suitable to assist the wearer. As a result, little effort is required by the wearer for performing the stand–sit–stand motions. The rotation of the thigh link of the developed exoskeleton was found to be suitable for performing the stand–sit–stand activity.

Place, publisher, year, edition, pages
Sage, 2022
Keywords
Knee exoskeleton, four-bar linkage, linear actuator, stand–sit–stand motion, bond graph modeling, experimental validation
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-37938 (URN)10.1177/00375497211073583 (DOI)000751418700001 ()2-s2.0-85124007439 (Scopus ID)
Available from: 2022-02-14 Created: 2022-02-14 Last updated: 2022-06-30Bibliographically approved
Masud, N., Senkic, D., Smith, C. & Isaksson, M. (2021). Modeling and control of a 4-ADOF upper-body exoskeleton with mechanically decoupled 3-D compliant arm-supports for improved-pHRI. Mechatronics (Oxford), 73, Article ID 102406.
Open this publication in new window or tab >>Modeling and control of a 4-ADOF upper-body exoskeleton with mechanically decoupled 3-D compliant arm-supports for improved-pHRI
2021 (English)In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 73, article id 102406Article in journal (Refereed) Published
Abstract [en]

Safe physical human-robotic interaction is a crucial concern for worn exoskeletons where lower weight requirement limits the number and size of actuators to be used. A novel control strategy is suggested in this paper for the low degree of freedom exoskeletons, by combining proposed mechanically decoupled passive-compliant arm-supports with active compliance, to achieve an improved and safer physical-human-robotic-interaction performance, while considering the practical limitations of low-power actuators. The approach is further improved with a novel vectoral-form of disturbance observer-based dynamic load-torque compensator, proposed to linearize and decouple the nonlinear human-machine dynamics effectively. The design of a four-degree of freedom exoskeleton test-rig that can assure the implementation of the proposed strategy is also shortly presented. It is shown through simulation and experimentation, that the use of proposed strategy results in an improved and safer physical human-robotic interaction, for the exoskeletons using limited-power actuators. It is also shown both through simulation and experimentation, that the proposed vectoral-form of disturbance based dynamic load-toque compensator, effectively outperforms the other traditional compensators in compensating the load-torques at the joints of the exoskeleton.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Assistive exoskeleton, Compliant supports, Serial manipulator, Upper-body, pHRI, Modeling and control
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-35249 (URN)10.1016/j.mechatronics.2020.102406 (DOI)000621215800010 ()2-s2.0-85100047112 (Scopus ID)
Available from: 2021-02-10 Created: 2021-02-10 Last updated: 2021-03-18Bibliographically approved
Andersson, R., Björsell, N. & Isaksson, M. (2021). Robots are a promising investment to fight pandemics. In: 2021 8th International Conference on Signal Processing and Integrated Networks (SPIN): . Paper presented at SPIN 2021 8th International Conference on Signal Processing and Integrated Networks, 26-27 August, Noida, India (pp. 458-463). IEEE
Open this publication in new window or tab >>Robots are a promising investment to fight pandemics
2021 (English)In: 2021 8th International Conference on Signal Processing and Integrated Networks (SPIN), IEEE , 2021, p. 458-463Conference paper, Published paper (Refereed)
Abstract [en]

Coronavirus caused pandemics as many viruses did through human history. The current pandemic causes overwhelmed healthcare system, locked down cities, and massive fatality among humans. Thus, different robots have been used since the COVID outbreak worldwide to reduce spreading infectious diseases and support frontline healthcare workers. This paper sets out the different robots implemented for hospital, non-hospital use, and possible use that can be deployed amidst the pandemic. A literature survey of versatile robots during COVID-19 is introduced. Roboticists contributed with wheeled and drone robots with various applications to assist medical care systems and society during the ongoing crisis. Pandemics are common throughout human history and difficult to avoid or prevent; thus, we intend to encourage societies, academia, engineers and innovators to invest more in robots that cannot catch the virus and consequently introduce beneficial solutions to fight such pandemic in the future.

Place, publisher, year, edition, pages
IEEE, 2021
Keywords
COVID-19; Drone; Exoskeleton; Frontline Workers; Monitoring Robots; Pandemic; Rehabilitation; Robots; Sanitising
National Category
Health Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-37208 (URN)10.1109/SPIN52536.2021.9566116 (DOI)2-s2.0-85126187085 (Scopus ID)978-1-6654-3564-2 (ISBN)
Conference
SPIN 2021 8th International Conference on Signal Processing and Integrated Networks, 26-27 August, Noida, India
Available from: 2021-10-21 Created: 2021-10-21 Last updated: 2023-02-17Bibliographically approved
Jain, P., Bera, T. K., Rafique, S., Singla, A. & Isaksson, M. (2020). Comparative study of knee joint torque estimations for linear and rotary actuators using bond graph approach for stand–sit–stand motions. International Journal of Advanced Robotic Systems, 17(5), 1-13
Open this publication in new window or tab >>Comparative study of knee joint torque estimations for linear and rotary actuators using bond graph approach for stand–sit–stand motions
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2020 (English)In: International Journal of Advanced Robotic Systems, ISSN 1729-8806, E-ISSN 1729-8814, Vol. 17, no 5, p. 1-13Article in journal (Refereed) Published
Abstract [en]

Stand–sit–stand (STS) motions are the most frequently performed activities of everyday life and require extensive movement of knee joint. People suffering from knee joint disorders face difficulties in performing this motion. The compact knee exoskeleton (KE) has proven to be a viable, less complex, and cheaper alternative to the available entire lower-, upper-, and full-body exoskeletons. With growing number of technical glitches and finite battery life problems, there exist risks of sudden failure of the actuator of KE that could be detrimental for the vulnerable users. To overcome this problem, there is a need to accommodate a backup actuator in KE which can continue providing assistance during movement if the primary actuator ceases to function. This article provides a performance comparison of a four-bar mechanism-driven KE that can accommodate both the linear and the rotary actuators. The modelling and simulation of the system are performed using the bond graph (BG) technique. The results successfully showed that both actuators offered desired ranges of motions needed for STS motion. Furthermore, the knee joint torques developed by the linear and rotary actuators were found to be 40 Nm and 57 Nm, respectively, which corresponds to 60% and 85% of the total torque required by the knee joint to perform STS motions, thereby reducing the user effort to 40% and 15%, respectively. Thus, both actuators are self-capable to provide necessary assistance at the knee joint even if the primary actuator ceases to work due to a sudden fault, the secondary actuator will provide the required rotation of the thigh link and will continue to deliver the assistive torque. The article also effectively shows the application of BG approach to model the multidisciplinary systems like KE as it conveniently models the system containing various elements in different energy domains.

Place, publisher, year, edition, pages
London: Sage Publications, 2020
Keywords
Knee exoskeleton, four-bar mechanism, linear actuator, rotary actuator, stand–sit–stand motions, knee joint torque, bond graph modelling
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
no Strategic Research Area (SFO)
Identifiers
urn:nbn:se:hig:diva-34157 (URN)10.1177/1729881420963742 (DOI)000582213500001 ()2-s2.0-85092616319 (Scopus ID)
Available from: 2020-10-20 Created: 2020-10-20 Last updated: 2020-11-12Bibliographically approved
Masud, N., Mattsson, P., Smith, C. & Isaksson, M. (2020). On stability and performance of disturbance observer-based-dynamic load torque compensator for assistive exoskeleton: A hybrid approach. Mechatronics (Oxford), 69, Article ID 102373.
Open this publication in new window or tab >>On stability and performance of disturbance observer-based-dynamic load torque compensator for assistive exoskeleton: A hybrid approach
2020 (English)In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 69, article id 102373Article in journal (Refereed) Published
Abstract [en]

A disturbance observer-based-dynamic load-torque compensator for current-controlled DC-drives, as joint actuator of assistive exoskeletons, has been recently proposed. It has been shown that this compensator can effectively linearize and decouple the coupled nonlinear dynamics of the human-exoskeleton system, by more effectively compensating the associated nonlinear load-torques of the exoskeleton at the joint level. In this paper, a detailed analysis of the current controlled DC drive-servo system using the said compensator, with respect to performance and stability is presented, highlighting the key factors and considerations affecting both the stability and performance of the compensated servo system. It is shown both theoretically and through simulation results that the stability of the compensated servo system is compromised as performance is increased and vice-versa. Based on the saturation state of the servo system, a new hybrid switching control strategy is then proposed to select stability or performance-based compensator and controller optimally. The strategy is then experimentally verified both at the joint and task space level by using the developed four active-degree of freedom exoskeleton test rig.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Assistive-exoskeleton, Performance, Stability, Disturbance observer, Load-torque
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-33337 (URN)10.1016/j.mechatronics.2020.102373 (DOI)000571817900010 ()2-s2.0-85087201583 (Scopus ID)
Note

This work was supported in part by the Ambient Assistance Living (AL) Program under Grant AAL-2013-6-042

Available from: 2020-08-18 Created: 2020-08-18 Last updated: 2020-10-16Bibliographically approved
Christensen, S., Bai, S., Rafique, S., Isaksson, M., O'Sullivan, L., Power, V. & Virk, G. S. (2019). AXO-SUIT: A Modular Full-Body Exoskeleton for Physical Assistance. In: Alessandro Gasparetto and Marco Ceccarelli (Ed.), Alessandro Gasparetto and Marco Ceccarelli (Ed.), Mechanism Design for Robotics: Proceedings of the 4th IFToMM Symposium on Mechanism Design for Robotics. Paper presented at MEDER: IFToMM Symposium on Mechanism Design for Robotics,11-13 September 2018, Udine, Italy (pp. 443-450). Paper presented at MEDER: IFToMM Symposium on Mechanism Design for Robotics,11-13 September 2018, Udine, Italy. Cham: Springer Netherlands, 66
Open this publication in new window or tab >>AXO-SUIT: A Modular Full-Body Exoskeleton for Physical Assistance
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2019 (English)In: Mechanism Design for Robotics: Proceedings of the 4th IFToMM Symposium on Mechanism Design for Robotics / [ed] Alessandro Gasparetto and Marco Ceccarelli, Cham: Springer Netherlands, 2019, Vol. 66, p. 443-450Chapter in book (Refereed)
Abstract [en]

This paper presents the design of a modular full-body assistive exoskeleton (FB-AXO) for older adults which was developed with funding under the AAL funded AXO-SUIT project. Processes used to formulate a prioritized set of functional and design requirements via close-end-user involvement are outlined and used in realizing the exoskeleton. Design of the resulting mechanics and electronics details for the lower and upper-body subsystems (LB-AXO and (UB-AXO)) are described. Innovative designs of shoulder and spine mechanisms are presented. TheFB-AXO system comprises 27 degrees of freedom, of which 17 are passive and 10 active. The exoskeleton assists full-body motions such as walking, standing, bending, as well as performing lifting and carrying tasks to assist older users performing tasks of daily living.

Place, publisher, year, edition, pages
Cham: Springer Netherlands, 2019
Series
Mechanisms and Machine Science, ISSN 22110984 ; 66
Keywords
Exoskeleton, Full Body, Lower Body, Upper Body, Assistance
National Category
Robotics
Identifiers
urn:nbn:se:hig:diva-27926 (URN)10.1007/978-3-030-00365-4_52 (DOI)000460585000052 ()2-s2.0-85052801351 (Scopus ID)978-3-030-00364-7 (ISBN)978-3-030-00365-4 (ISBN)
Conference
MEDER: IFToMM Symposium on Mechanism Design for Robotics,11-13 September 2018, Udine, Italy
Funder
Vinnova, 2014-05953
Note

Papers presented at IFToMM Symposium on Mechanism Design for Robotics, 11-13 August 2018, Udine, Italy

Funding:

- EU AAL Programme- Innovation Fund Denmark- Agentschap Innoveren Ondernemen- Enterprise Ireland 

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2020-10-28Bibliographically approved
Masud, N., Smith, C. & Isaksson, M. (2018). Disturbance observer based dynamic load torque compensator for assistive exoskeletons. Mechatronics (Oxford), 54, 78-93
Open this publication in new window or tab >>Disturbance observer based dynamic load torque compensator for assistive exoskeletons
2018 (English)In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 54, p. 78-93Article in journal (Refereed) Published
Abstract [en]

In assistive robotics applications, the human limb is attached intimately to the robotic exoskeleton. The coupled dynamics of the human-exoskeleton system are highly nonlinear and uncertain, and effectively appear as uncertain load-torques at the joint actuators of the exoskeleton. This uncertainty makes the application of standard computed torque techniques quite challenging. Furthermore, the need for safe human interaction severely limits the gear ratio of the actuators. With small gear ratios, the uncertain joint load-torques cannot be ignored and need to be effectively compensated. A novel disturbance observer based dynamic load-torque compensator is hereby proposed and analysed for the current controlled DC-drive actuators of the exoskeleton, to effectively compensate the said uncertain load-torques at the joint level. The feedforward dynamic load-torque compensator is proposed based on the higher order dynamic model of the current controlled DC-drive. The dynamic load-torque compensator based current controlled DC-drive is then combined with a tailored feedback disturbance observer to further improve the compensation performance in the presence of drive parametric uncertainty. The proposed compensator structure is shown both theoretically and practically to give significantly improved performance w.r.t disturbance observer compensator alone and classical static load-torque compensator, for rated load-torque frequencies up to 1.6 Hz, which is a typical joint frequency bound for normal daily activities for elderly. It is also shown theoretically that the proposed compensator achieves the improved performance with comparable reference current requirement for the current controlled DC-drive.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Disturbance observer, Exoskeleton, Load torque compensator, Serial manipulator, Actuators, DC motors, Dynamic loads, Electric machine control, Electric machine theory, Joints (anatomy), Manipulators, Robotics, Torque, Torque measurement, Application of standards, Compensation performance, Compensator structure, Higher-order dynamics, Load torques, Parametric uncertainties, Serial manipulators, Exoskeleton (Robotics)
National Category
Robotics
Identifiers
urn:nbn:se:hig:diva-27633 (URN)10.1016/j.mechatronics.2018.07.003 (DOI)000446949100007 ()2-s2.0-85050674987 (Scopus ID)
Note

Ambient Assisted Living (AAL) Program  Grant no: AAL-2013-6-042

Available from: 2018-08-14 Created: 2018-08-14 Last updated: 2018-11-26Bibliographically approved
Khan, Z. A., Zenteno, E., Händel, P. & Isaksson, M. (2018). Extraction of the Third-Order 3x3 MIMO Volterra Kernel Outputs Using Multitone Signals. IEEE transactions on microwave theory and techniques, 66(11), 4985-4999
Open this publication in new window or tab >>Extraction of the Third-Order 3x3 MIMO Volterra Kernel Outputs Using Multitone Signals
2018 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 66, no 11, p. 4985-4999Article in journal (Refereed) Published
Abstract [en]

This paper uses multitone signals to simplify the analysis of 3×3 multiple-input multiple-output (MIMO) Volterra systems by isolating the third-order kernel outputs from each other. Multitone signals fed to an MIMO Volterra system yield a spectrum that is a permutation of the sums of the input signal tones. This a priori knowledge is used to design multitone signals such that the third-order kernel outputs are isolated in the frequency domain. The signals are designed by deriving the conditions for the offset and spacing of the input frequency grids. The proposed technique is then validated for the six possible configurations of a 3x3 RF MIMO transmitter impaired by crosstalk effects. The proposed multitone signal design is used to extract the third-order kernel outputs, and their relative contributions are analyzed to determine the dominant crosstalk effects for each configuration.

Place, publisher, year, edition, pages
IEEE, 2018
Keywords
Crosstalk; hardware impairments; multiple-input multiple-output (MIMO); multitone signals; Volterra kernels
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-27812 (URN)10.1109/TMTT.2018.2854186 (DOI)000449354500028 ()2-s2.0-85052719621 (Scopus ID)
Available from: 2018-09-01 Created: 2018-09-01 Last updated: 2022-10-31Bibliographically approved
Projects
Radio frequency measurement technology for weakly nonlinear systems [2009-02977_VR]; University of Gävle
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