Novel Robotic System for Joint Mechanical Tests Using Velocity-Impedance Control

Fujie, Hiromichi; Yagi, Hitoshi

doi:10.1115/sbc2011-53884

Cited by 4 publications

(6 citation statements)

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“…Among the unconstrained control methods, a similar trend was also found: the smaller the RMS values of the constraining forces and moments, the bigger the maximum displacement, and thus the joint laxity. These results suggest that the control of the RJTS to reduce as much as possible the constraining forces and moments during unconstrained laxity tests for more accurately determining the joint stiffness characteristics is essential for various clinical applications, such as establishing baseline data for normal joint biomechanics [ 15 – 17 , 24 , 29 , 30 ], exploring injury biomechanics (e.g., ligament ruptures, [ 18 ]), and evaluating existing and new treatment methods (e.g., reconstructed ligaments and total knee replacements [ 7 , 18 ]. From the current results, it appears that FPHFM and FPA are capable of improving FPH in reducing the constraining forces and moments, but the FPHFM is better than FPA when considering both the residual constraining loads and the total control time.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, self-designed mechanisms/structures are needed [ 22 , 23 ]. For example, Fujie et al [ 24 ] developed a robotic system of rigid body/structure that allows high-rate force-position control of the knee joint using a velocity-impedance control. The velocity impedance strategy for the continuous servo system used force control with modified velocity-impedance control, and position control with velocity control [ 25 ].…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of three force-position hybrid control methods for a robot-based biological joint-testing system

Hsieh

et al. 2016

BioMed Eng OnLine

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BackgroundRobot-based joint-testing systems (RJTS) can be used to perform unconstrained laxity tests, measuring the stiffness of a degree of freedom (DOF) of the joint at a fixed flexion angle while allowing the other DOFs unconstrained movement. Previous studies using the force-position hybrid (FPH) control method proposed by Fujie et al. (J Biomech Eng 115(3):211–7, 1993) focused on anterior/posterior tests. Its convergence and applicability on other clinically relevant DOFs such as valgus/varus have not been demonstrated. The current s1tudy aimed to develop a 6-DOF RJTS using an industrial robot, to propose two new force-position hybrid control methods, and to evaluate the performance of the methods and FPH in controlling the RJTS for anterior/posterior and valgus/varus laxity tests of the knee joint.MethodsAn RJTS was developed using an industrial 6-DOF robot with a 6-component load-cell attached at the effector. The performances of FPH and two new control methods, namely force-position alternate control (FPA) and force-position hybrid control with force-moment control (FPHFM), for unconstrained anterior/posterior and valgus/varus laxity tests were evaluated and compared with traditional constrained tests (CT) in terms of the number of control iterations, total time and the constraining forces and moments.ResultsAs opposed to CT, the other three control methods successfully reduced the constraining forces and moments for both anterior/posterior and valgus/varus tests, FPHFM being the best followed in order by FPA and FPH. FPHFM had root-mean-squared constraining forces and moments of less than 2.2 N and 0.09 Nm, respectively at 0° flexion, and 2.3 N and 0.14 Nm at 30° flexion. The corresponding values for FPH were 8.5 N and 0.33 Nm, and 11.5 N and 0.45 Nm, respectively. Given the same control parameters including the compliance matrix, FPHFM and FPA reduced the constraining loads of FPH at the expense of additional control iterations, and thus increased total time, FPA taking about 10 % longer than FPHFM.ConclusionsThe FPHFM would be the best choice among the methods considered when longer total time is acceptable in the intended clinical applications. The current results will be useful for selecting a force-position hybrid control method for unconstrained laxity tests using an RJTS.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluation of three force-position hybrid control methods for a robot-based biological joint-testing system

Hsieh

et al. 2016

BioMed Eng OnLine

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“…The robotic simulator system consisted of a 6‐degrees of freedom manipulator consisting of three translational/rotational actuators, servo‐motor controllers, a 6‐degrees of freedom universal force/moment sensor (UFS), and a control computer [5‐10, 22, 23, 25]. The maximum clamp‐to‐clamp compliance with the knee extended was 321 N/mm in the medial–lateral direction, 424 N/mm in the anterior–posterior direction, and 814 N/mm in the proximal–distal direction [10]. The force sensor resolution was 0.01–0.02 N for forces and 0.001 N m for torques [10, 25].…”

Section: Methodsmentioning

confidence: 99%

“…The maximum clamp‐to‐clamp compliance with the knee extended was 321 N/mm in the medial–lateral direction, 424 N/mm in the anterior–posterior direction, and 814 N/mm in the proximal–distal direction [10]. The force sensor resolution was 0.01–0.02 N for forces and 0.001 N m for torques [10, 25]. The test–retest reliability of this robotic system was ± 0.006 mm in translation and ± 0.03° in rotation for reproducing the paths [10, 25].…”

Section: Methodsmentioning

confidence: 99%

A longitudinal tear in the medial meniscal body decreased the in situ meniscus force under an axial load

Tachibana

Mae

Shino³

et al. 2019

Knee Surg Sports Traumatol Arthrosc

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Purpose To clarify the effect of longitudinal tears of the medial meniscus on the in situ meniscus force and the tibiofemoral relationship under axial load. Methods Twenty-one intact porcine knees were mounted on a 6-degrees of freedom robotic system, and the force and threedimensional path of the knee joints were recorded during three cycles under a 250-N axial load at 30°, 60°, 90° and 120° of knee flexion. They were divided into three groups of seven knees with longitudinal tears in the middle to the posterior segment of the medial meniscus based on the tear site: rim, outer one-third and inner one-third of the meniscal body. After creating tears, the same tests were performed. Finally, all paths were reproduced after total medial meniscectomy, and the in situ force of the medial meniscus was calculated based on the principle of superposition. Results With a longitudinal tear, the in situ force of the medial meniscus was significantly decreased at 60°, 90° and 120° of knee flexion, regardless of the tear site. The decrement was greater with a tear in the meniscal body than a tear in the rim. A longitudinal tear in the meniscal body caused a significantly greater tibial varus rotation than a tear in the rim at all flexion angles. Conclusion Longitudinal tears significantly decreased the in situ force of the medial meniscus. Tears in the meniscal body caused a larger decrease of the in situ meniscus force and greater varus tibial rotation than tears in the rim.

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“…Fujie and Yagi, 2011) ．しかし，旧型システムの剛性は，直動自由度については 320～814 N/mm，回転自由度については 90～168 Nm/deg 程度であり，高荷重の試験が困難であった．また，制御プログラムを PC の Windows…”

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Development of a novel robotic system for joint mechanical tests using a real-time controller

Kimura

Fujie

2015

Transactions of the JSME (In Japanese)

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Application of robotic systems to the field of joint biomechanics studies has been performing in the last 2 decades. While a variety of studies have employed commercially available articulated robots we have designed and developed a material testing machine-like 6-degree of freedom (DOF) robotic system for higher load capacity and accuracy. The previous system consists of serially linked 2 translational and 3 rotational axes and a translational axis. All the servomotors at the 6 axes are controlled by a PC through a high-speed motion network. In the present study, we developed a novel 6-DOF robotic system that has a decoupled mechanism consisting of serially linked 3 translational axes and serially linked 3 rotational axes. All the servomotors at the 6 axes are controlled by a real-time controller through the EtherNet and EtherCAT. With knee joints fixed to the robotic system, either force control or position control can be applied with respect to the 6-DOF knee joint coordinate system. The velocity-impedance control was modified and applied to the force control while the velocity control was applied to the position control. The clamp-to-clamp stiffness of the novel robotic system was 541-1027 N/m and 262-355 Nm/rad which are more than 1.5 times higher than those of previous system. Responses to a step-function force input and a ramp-function force input were faster and more precise in the novel system than in the previous system. Moreover, joint forces and moments during 2-DOF and 6-DOF joint loading tests were controlled more precisely in the novel system than in the previous system. These results indicate the superiority of the novel robotic system over previously developed robotic systems. We believe that, with the system, it is possible to simulate physiological situations of the knee joint such as slow gait, standing up from a chair, and so on.

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Novel Robotic System for Joint Mechanical Tests Using Velocity-Impedance Control

Cited by 4 publications

References 0 publications

Evaluation of three force-position hybrid control methods for a robot-based biological joint-testing system

Evaluation of three force-position hybrid control methods for a robot-based biological joint-testing system

A longitudinal tear in the medial meniscal body decreased the in situ meniscus force under an axial load

Development of a novel robotic system for joint mechanical tests using a real-time controller

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