A flexible controller for a Stewart platform

Graf, René; Vierling, R.; Dillmann, Rüdiger

doi:10.1109/kes.1998.725892

Cited by 10 publications

(9 citation statements)

References 3 publications

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“…23 This robotic motion phantom follows the Stewart-Gough platform archetype and uses inverse kinematics to control a mobile top platform relative to a stationary bottom platform both translationally and rotationally by precisely modulating the six struts, or linear actuators, which connect the two platforms. 24,25 Previous research focused on the design, production, and evaluation of this system demonstrated the control capabilities to be less than 0.22 mm translationally and 0.16 • rotationally. 23 As such, the highly F.…”

Section: A Experimental Setupmentioning

confidence: 99%

Spatial and rotational quality assurance of 6DOF patient tracking systems

et al. 2016

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Purpose: External tracking systems used for patient positioning and motion monitoring during radiotherapy are now capable of detecting both translations and rotations. In this work, the authors develop a novel technique to evaluate the 6 degree of freedom 6(DOF) (translations and rotations) performance of external motion tracking systems. The authors apply this methodology to an infrared marker tracking system and two 3D optical surface mapping systems in a common tumor 6DOF workspace. Methods: An in-house designed and built 6DOF parallel kinematics robotic motion phantom was used to perform motions with sub-millimeter and subdegree accuracy in a 6DOF workspace. An infrared marker tracking system was first used to validate a calibration algorithm which associates the motion phantom coordinate frame to the camera frame. The 6DOF positions of the mobile robotic system in this space were then tracked and recorded independently by an optical surface tracking system after a cranial phantom was rigidly fixed to the moveable platform of the robotic stage. The calibration methodology was first employed, followed by a comprehensive 6DOF trajectory evaluation, which spanned a full range of positions and orientations in a 20 × 20 × 16 mm and 5• × 5 • × 5• workspace. The intended input motions were compared to the calibrated 6DOF measured points. Results:The technique found the accuracy of the infrared (IR) marker tracking system to have maximal root-mean square error (RMSE) values of 0.18, 0.25, 0.07 mm, 0.05• , 0.05 • , and 0.09• in left-right (LR), superior-inferior (SI), anterior-posterior (AP), pitch, roll, and yaw, respectively, comparing the intended 6DOF position and the measured position by the IR camera. Similarly, the 6DOF RSME discrepancy for the HD optical surface tracker yielded maximal values of 0.46, 0.60, 0.54 mm, 0.06• , 0.11 • , and 0.08 • in LR, SI, AP, pitch, roll, and yaw, respectively, over the same 6DOF evaluative workspace. An earlier generation 3D optical surface tracking unit was observed to have worse tracking capabilities than both the IR camera unit and the newer 3D surface tracking system with maximal RMSE of 0.69, 0.74, 0.47 mm, 0.28• , 0.19 • , and 0.18 • , in LR, SI, AP, pitch, roll, and yaw, respectively, in the same 6DOF evaluation space. Conclusions: The proposed technique was found to be effective at evaluating the performance of 6DOF patient tracking systems. All observed optical tracking systems were found to exhibit tracking capabilities at the sub-millimeter and subdegree level within a 6DOF workspace. C 2016 American Association of Physicists in Medicine. [http://dx

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Section: A Experimental Setupmentioning

confidence: 99%

Spatial and rotational quality assurance of 6DOF patient tracking systems

et al. 2016

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“…The first one is based on the legs lengths tracking control and is called joint space control (Salcudean et al, 1994;Graf et al, 1998). On the contrary, the second one is based on the position and orientation tracking control and is called cartesian space control (Becerra-Vargas et al, 2009;Koekebakker, 2001).…”

Section: Motion Base Controller Designmentioning

confidence: 99%

“…Each leg is composed of a prismatic joint (i.e an electromechanical or electrohydraulic actuator), one passive universal joint and one passive spherical joint making connection with the base and the moving platform, respectively, as shown in Fig Most motion control schemes concerning flight simulator motion bases are focused on the washout-filter (Nahon and Reid, 1990), forward and inverse kinematics; and an independent joint linear controller is implemented for each actuator (Salcudean et al, 1994;Graf et al, 1998). On the other hand, the effects of the motion-base dynamics are ignored or a linearized model of motion-base dynamics is used (Idan and Sahar, 1996).…”

Section: Introductionmentioning

confidence: 99%

Application of H∞ theory to a 6 DOF flight simulator motion base

Becerra-Vargas¹,

Belo²

2012

J. Braz. Soc. Mech. Sci. & Eng.

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The purpose of this study is to apply inverse dynamics control for a six degree of freedom flight simulator motion system. Imperfect compensation of the inverse dynamic control is intentionally introduced in order to simplify the implementation of this approach. The control strategy is applied in the outer loop of the inverse dynamic control to counteract the effects of imperfect compensation. The control strategy is designed using H ∞ theory. Forward and inverse kinematics and full dynamic model of a six degrees of freedom motion base driven by electromechanical actuators are briefly presented. Describing function, acceleration step response and some maneuvers computed from the washout filter were used to evaluate the performance of the controllers.

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“…The fluid's movement was represented by a pendulum model. Another active method for the compensation of accelerations was presented in [11,12]. Accelerations which affect a load placed on a mobile platform were actively com pensated by use of a parallel kinematics built underneath.…”

Section: State Of the Artmentioning

confidence: 99%

Tremor compensation by use of a mechatronic cup holder

Fischer

Schraufstetter

Richter

et al. 2010

Proceedings of the 4th International ICST Conference on Pervasive Computing Technologies for Healthcare

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In this p aper a new assistive device for p ersons suffer ing tremor disease is presented. It should hel p those people to get along with the everyday life situation of consuming beverages and replace the feeding cups currently used. The cu p holder is built u p as a mechatronic system. It consists of a kinematic structure sustaining a standard cu p as well as elec tronic and software components. The cup is moved by the device in order to compensate linear and rotational accelerations as well as tilt induced by a p erson's tremor. For this p ur p ose the charac teristics of the fast and large scaled tremor movements of the p atient's hand are measured first. By use of the inverse kinemat ics calculated for the system and a method for the modelling of the liquid's movement, necessary reactions of the cu p holder are deduced. Using this information the device's motors are actuated to avoid spillage of the liquid. The underlying calculations are run on a micro controller integrated in the system. An experiment was conducted to validate the function of the system. For this purpose an industrial robot was used to apply common tremor frequencies and am p litudes to the cup holder. It was shown that by use of the compensatory cup holder the s pill age of the beverage can be eliminated at a wide range of different tremors.

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A flexible controller for a Stewart platform

Cited by 10 publications

References 3 publications

Spatial and rotational quality assurance of 6DOF patient tracking systems

Spatial and rotational quality assurance of 6DOF patient tracking systems

Application of H∞ theory to a 6 DOF flight simulator motion base

Tremor compensation by use of a mechatronic cup holder

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