Active Constraints/Virtual Fixtures: A Survey

Bowyer, Stuart A; Davies, Brian; Baena, Ferdinando Rodriguez y

doi:10.1109/tro.2013.2283410

Cited by 273 publications

(182 citation statements)

References 90 publications

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“…Cobots' operation principle is based on creating virtual guiding surfaces, for that purpose, continuously variable transmissions (CVTs) connected to the joints of the links conforming the kinematic chain are used [3,7]. A figure representing the operating principle of a human-cobot system (cobotic system) is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Free Kinematic Singularity Controller for a Planetary Gear Based Cobot

Mendoza-Trejo

Padilla-García

Cruz-Villar

et al. 2018

Int J of Soc Robotics

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Cobots are devices that interact with human operators to execute tasks in non deterministic and unstructured environments. Controlling a cobot can be seen as a path following problem, such that the controller restricts the motion of the device to the desired trajectory, impeding motion in orthogonal directions. Velocity control is a common strategy for path following, in the particular case of cobots, it allows the user to modulate the speed of the device while the controller changes the direction of motion as required. However, velocity controls are not suitable when the controller works or crosses through kinematic singularities, where bad conditioning of the velocity arises. In this paper a velocity control for cobots is presented, that is free of Jacobian singularities. The performance of the proposed controller is shown by experimental results in a two degree of freedom cobot with differential gear trains in serial configuration. Experimental results show that by using the proposed controller, cobotic systems performance is not affected by kinematic singularities, so, cobots can properly work in their whole workspace.

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Section: Introductionmentioning

confidence: 99%

Free Kinematic Singularity Controller for a Planetary Gear Based Cobot

Mendoza-Trejo

Padilla-García

Cruz-Villar

et al. 2018

Int J of Soc Robotics

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“…AC/VF allow semi-automatic robot telemanipulation, wherein the complexity of the inverse kinematics is hidden to the user while he/ she is guided to avoid collisions with the anatomy or unstable configurations. AC comprise three components: a) constraint generation, b) constraint evaluation, and c) constraint enforcement [19].…”

Section: Introductionmentioning

confidence: 99%

Implicit active constraints for safe and effective guidance of unstable concentric tube robots

Leibrandt

Bergeles

Yang

2016

2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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Abstract-Safe and effective telemanipulation of concentric tube robots is hindered by their complex, non-intuitive kinematics. In order for clinicians to operate these robots naturally, guidance schemes in the form of attractive and repulsive constraints can simplify task execution. The real-time seamless calculation and application of guidance, however, requires computationally efficient algorithms that solve the non-linear inverse kinematics of the robot and guarantee that the commanded robot configuration is stable and sufficiently away from the anatomy. This paper presents a multi-processor framework that allows on-the-fly calculation of optimal safe paths based on rapid workspace and roadmap precomputation. The realtime nature of the developed software enables complex guidance constraints to be implemented with minimal computational overhead. A clinically challenging user study demonstrates that the incorporated guiding constraints are highly beneficial for fast and accurate navigation with concentric tube robots.

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“…In an impedance-type virtual fixture scheme, the haptic force is proportional to the difference between the actual and desired positions at the slave end-effector, and its direction is orthogonal to the intended trajectory of the haptic device [30][31][32] . No information about the position of the slave is used in virtual fixture scheme.…”

Section: Introductionmentioning

confidence: 99%