Modeling and control of inherently safe robots with variable stiffness links

Song, Siyang; Zeng, Xianpai; She, Yu; Wang, Junmin; Su, Hai‐Jun

doi:10.1016/j.robot.2019.07.017

Cited by 14 publications

(14 citation statements)

References 31 publications

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“…As we discussed in Sec. 2.2, the dynamics of the VSA robot and VSL robot both can be denoted by the Euler-Lagrange equation (9). However, the modeling of the VSL robot is more complicated than the VSA.…”

Section: Examplementioning

confidence: 99%

“…However, these requirements sacrifice robot speed and efficiency. To have a better tradeoff between the safety and speed, there have been several interesting concepts toward these two goals, ranging from mechanical designs [2][3][4], controls [5][6][7][8][9], to motion planning [10][11][12]. Among those approaches, the variable stiffness (VS) concept is promising because it may address both safety and efficiency simultaneously.…”

Section: Introductionmentioning

confidence: 99%

“…In Ref. [9], by employing the proposed control and planning methods, a VSL arm can be safer and faster than the traditional robot. In Ref.…”

Section: Introductionmentioning

confidence: 99%

“…[19] and its stiffness can change up to 17 times, which is promising for pHRI applications. These efforts have shown the benefits of VS robots for pHRI applications from different aspects, such as impact reduction [15,17] and faster work speed [2,9]. However, an important question that has not been answered in these studies is: how do we design the mass and flexibility properties of a VS robot to have significant benefits ? We already know that large impact reduction can let VS robots move faster in the fast-and-soft mode.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Toward Tradeoff Between Impact Force Reduction and Maximum Safe Speed: Dynamic Parameter Optimization of Variable Stiffness Robots

Song

She

Wang

et al. 2020

Journal of Mechanisms and Robotics

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Variable stiffness robots may provide an effective way of trading-off between safety and speed during physical human–robot interaction. In such a compromise, the impact force reduction capability and maximum safe speed are two key performance measures. To quantitatively study how dynamic parameters such as mass, inertia, and stiffness affect these two performance measures, performance indices for impact force reduction capability and maximum speed of variable stiffness robots are proposed based on the impact ellipsoid in this paper. The proposed performance indices consider different impact directions and kinematic configurations in the large. Combining the two performance indices, the global performance of variable stiffness robots is defined. A two-step optimization method is designed to achieve this global performance. A two-link variable stiffness link robot example is provided to show the efficacy of the proposed method.

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Section: Examplementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…In Ref. [9], by employing the proposed control and planning methods, a VSL arm can be safer and faster than the traditional robot. In Ref.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Toward Tradeoff Between Impact Force Reduction and Maximum Safe Speed: Dynamic Parameter Optimization of Variable Stiffness Robots

Song

She

Wang

et al. 2020

Journal of Mechanisms and Robotics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Although safety is of paramount importance when closely collaborating with humans, position control is critical to perform tasks such as pick-and-place operations. Current studies have investigated the performance of a single VSL [21] and configuration combining the VSL with one Degree of Freedom (DoF) [22]. To the best of the authors knowledge, no work exists on exploring position control based on variable stiffness in VSL robotic manipulators.…”

Section: Introductionmentioning

confidence: 99%

Open-Loop Position Control in Collaborative, Modular Variable-Stiffness-Link (VSL) Robots

Gandarias

Wang

Stilli

et al. 2020

IEEE Robot. Autom. Lett.

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Collaborative robots (cobots) open up new avenues in the fields of industrial robotics and physical Human-Robot Interaction (pHRI) as they are suitable to work in close approximation and in collaboration with humans. The integration and control of variable stiffness elements allow inherently safe interaction. Apart from notable work on Variable Stiffness Actuators, the concept of Variable-Stiffness-Link (VSL) manipulators promises safety improvements in cases of unintentional physical collisions. However, position control of these type of robotic manipulators is challenging for critical task-oriented motions (e.g., pick and place). Hence, the study of open-loop position control for VSL robots is crucial to achieve high levels of safety, accuracy and hardware cost-efficiency in pHRI applications. In this paper, we propose a hybrid, learning based kinematic modelling approach to improve the performance of traditional open-loop position controllers for a modular, collaborative VSL robot. We show that our approach improves the performance of traditional open-loop position controllers for robots with VSL and compensates for position errors, in particular, for lower stiffness values inside the links: Using our upgraded and modular robot, two experiments have been carried out to evaluate the behaviour of the robot during taskoriented motions. Results show that traditional model-based kinematics are not able to accurately control the position of the end-effector: the position error increases with higher loads and lower pressures inside the VSLs. On the other hand, we demonstrate that, using our approach, the VSL robot can outperform the position control compared to a robotic manipulator with 3D printed rigid links.

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Linear Motor Command Tracking: A Novel Immersion and Invariance Adaptive Control Method with Arctangent-Function-Based Parameter Projection

et al. 2022

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Modeling and control of inherently safe robots with variable stiffness links

Cited by 14 publications

References 31 publications

Toward Tradeoff Between Impact Force Reduction and Maximum Safe Speed: Dynamic Parameter Optimization of Variable Stiffness Robots

Toward Tradeoff Between Impact Force Reduction and Maximum Safe Speed: Dynamic Parameter Optimization of Variable Stiffness Robots

Open-Loop Position Control in Collaborative, Modular Variable-Stiffness-Link (VSL) Robots

Linear Motor Command Tracking: A Novel Immersion and Invariance Adaptive Control Method with Arctangent-Function-Based Parameter Projection

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