Compliant Control of Single Tendon-Sheath Actuators Applied to a Robotic Manipulator

Yin, Meng; Wu, Haoting; Xu, Zhigang; Han, Wei; Zhao, Zhiliang

doi:10.1109/access.2020.2973173

Cited by 12 publications

(10 citation statements)

References 36 publications

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“…The faster of signals are, the more non-linear and hysteresis have been performed. This may be due to the fact that the response characteristics of the Bowden cable determine the output characteristics of the model, which is a problem that many previous studies [32,33] have also encountered. Hence, it should consider the signal frequency when the Bowden cable system has been utilized to the transmission system with continuously changing requirements.…”

Section: Discussionmentioning

confidence: 99%

Control of flexible knee joint exoskeleton robot based on dynamic model

Liu

Zhou

et al. 2022

Robotica

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Summary The knee joint plays a significant role in ground clearness, which is a crucial subtask of normal walking and avoiding falls. While post-stroke survivors are often faced with muscle weakness during walking, which leads to inadequate knee flexion. The lack of ground clearance caused by inadequate knee flexion will severely impede walking, increase metabolic exertion, and increase the risk of falls. A compliant exoskeleton robot possesses more favorable edges than other rigid ones in lightweight, safety, sense of comfort, and so on. We developed a new type of soft exoskeleton robot to assist the knee joint to achieve desired movements with Bowden cable transmitting force and torque. With the agonist–antagonist driving method, like a group of muscles working, we have explored dual-motors structure to realize the knee flexion function. It has built a standard dynamic model to analyze stability and realize the control law. We have conducted simulation and prototype experiments to verify the feasibility and usefulness of our method. The results show that the device can compensate for the lack of the knee joint driving force and realize the reference movement. Finally, we concluded that our method is a desirable way, and the scheme could improve the knee flexion ability and clearing ground.

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Section: Discussionmentioning

confidence: 99%

Control of flexible knee joint exoskeleton robot based on dynamic model

Liu

Zhou

et al. 2022

Robotica

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“…The determination of the position parameters of the joint parts [5] is based on independent measurements using dual encoders mounted on the drive motor and the drive joint. In addition, in [6] it is proposed to calibrate manipulator positions by QR code.…”

Section: Analysis Of Recent Studies and Publicationsmentioning

confidence: 99%

Development and Study of the Operation of the Module for Determining the Orientation of the Manipulator Joint

Nevliudov

Novoselov

Sychova

2022

ITSSI

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In the field of mechatronic systems, manipulators are often used for automated assembly of products, welding, painting parts and more. An important task is to optimize the travel time along a given trajectory of the manipulator. To solve this problem, it is necessary not only to accurately estimate the speed of the manipulator nodes, but also to provide a linear characteristic of the assessment of the position of the mechanism in a wide range of speeds. The matter of the article are methods for determining the orientation of the joint of the manipulator. The goal of the work is to develop a module for determining the orientation of the joint of the manipulator and study its operation in order to determine the suitability subject of the structure for practical use. The following tasks are solved in the article: to investigate the principles of determining the orientation of the joints of industrial robots; choose the design of the orientation determination module; develop an algorithm for determining the position of the joint at any time; perform experimental studies of the position determination module in order to confirm the suitability of the structure for practical use. The following methods used are: experimental research was conducted on a real object - a model of the manipulator joint, created using methods and tools of 3D prototyping; to determine the position of the joint of the manipulator used methods of processing signals received from sensors; processing of experimental results and calculation of values of errors of positioning of a joint of the manipulator is based on methods of the statistical analysis of random sizes. The following results were obtained: the principles of determining the orientation of the joints of industrial robots were studied; the design is developed and the module of definition of orientation of a joint of the manipulator is created; developed an algorithm for determining the position of the joint at any time; the suitability of the design for practical use has been experimentally confirmed. Conclusions: in this paper, two variants of the sensor design are proposed to determine the absolute angle of rotation of the manipulator joint: resistive and magnetic. The proposed design of the resistive sensor was non-technological and much larger than the design of the magnetic sensor. The data obtained in the process of conducting experimental studies of the proposed method of measuring the angle of rotation of the mechanical gearbox of the manipulator joint indicate a fairly accurate determination of the angle using a magnetic sensor. The calculated measurement error was less than 1.4 degrees. The results of the experiment also showed that in addition to the radial direction of movement of the gearbox of the manipulator joint there is a significant displacement along the working plane, and in some cases, such displacements are chaotic. This is due to some defects and imperfections of the surface of the manufactured parts of the joint model used in research.

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“…The nonlinear friction in the Bowden inner cable and outer sheath is amajor source of hysteresis and phase delay of the transmission system. Studies have shown that a significant amount of the motor torque is generated to overcome the friction of the Bowden transmission cable [ 19 ].One way to address this problem is to use servo motors with very high power output and fast responses, which could reduce the influence of frictional disturbance of the Bowden cables to some extent, even when a basic PID controller is used. Such an approach, however, usually requires a large off-board platform to mount the bulkyservo motors and amplifiers, which prevents the outdoor and portable application of the soft exoskeleton system [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

Learning-Based Repetitive Control of a Bowden-Cable-Actuated Exoskeleton with Frictional Hysteresis

et al. 2022

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Bowden-cable-actuated soft exoskeleton robots are known for their light weight and flexibility of power transmission during rehabilitation training or movement assistance for humans. However, friction-induced nonlinearity of the Bowden transmission cable and gearbox backlash pose great challenges forprecise tracking control of the exoskeleton robot. In this paper, we proposed the design of a learning-based repetitive controller which could compensate for the non-linearcable friction and gearbox backlash in an iterative manner. Unlike most of the previous control schemes, the presented controller does not require apriori knowledge or intensive modeling of the friction and backlash inside the exoskeleton transmission system. Instead, it uses the iterative learning control (ILC)to adaptively update the reference trajectory so that theoutput hysteresis caused by friction and backlashis minimized. In particular, a digital phase-lead compensator wasdesigned and integrated with the ILC to address the issue of backlash delay and improve the stability and tracking performance. Experimental results showed an average of seveniterations for the convergence of learningand a 91.1% reduction in the RMS tracking error (~1.37 deg) compared withthe conventional PD control. The proposed controller design offers promising options for the realization of lightweight, wearable exoskeletons with high tracking accuracies.

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Compliant Control of Single Tendon-Sheath Actuators Applied to a Robotic Manipulator

Cited by 12 publications

References 36 publications

Control of flexible knee joint exoskeleton robot based on dynamic model

Control of flexible knee joint exoskeleton robot based on dynamic model

Development and Study of the Operation of the Module for Determining the Orientation of the Manipulator Joint

Learning-Based Repetitive Control of a Bowden-Cable-Actuated Exoskeleton with Frictional Hysteresis

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