Absolute Position Control Research Articles

Deterministic self‐organization: Ordered positioning of InAs quantum dots by self‐organized anisotropic strain engineering on patterned GaAs (311)B

AbstractLaterally ordered InGaAs quantum dot (QD) arrays, InAs QD molecules, and single InAs QDs in a spot‐like periodic arrangement are created by self‐organized anisotropic strain engineering of InGaAs/GaAs superlattice (SL) templates on planar GaAs (311)B substrates in molecular beam epitaxy. On shallow‐ and deep‐patterned substrates the respectively generated steps and facets guide the self‐organization process during SL template formation to create more complex ordering such as periodic stripes, depending on pattern design. Here we demonstrate for patterns such as shallow‐ and deepetched round holes and deep‐etched zigzag mesas that the self‐organized periodic arrangement of QD molecules and single QDs is spatially locked to the pattern sidewalls and corners. This extends the concept of guided self‐organization to deterministic self‐organization. Absolute position control of the QDs is achieved without one‐to‐one pattern definition. This guarantees the excellent arrangement control of the ordered QD molecules and single QDs with strong photoluminescence emission up to room temperature, which is required for future quantum functional devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Gradient Induced Motion Control of Drifting Solitary Structures in a Nonlinear Optical Single Feedback Experiment

We realize an absolute position control of drifting dissipative optical solitons by injecting an incoherent amplitude parameter gradient onto the nonlinear optical system. This allows for two-dimensional, arbitrary control patterns. The control of the soliton drift velocity is studied applying a periodic, hexagonally shaped modulation. The guiding of dissipative solitons by one- and two-dimensional parameter modulations is demonstrated. Furthermore, one-dimensional, line-shaped parameter modulations are designed to act as barriers for dissipative solitons, allowing implementations of position selectors for solitons. The interaction of dissipative optical solitons with barriers is studied for different barrier parameters.

An approach to absolute position control based on object coordinate

This paper describes accurate position control in an object coordinate system. When motion control of an industrial robot placed in a global coordinate system is taken to be in an object coordinate system, it is preferable and convenient to decide its motion by having the operator teach the robot. However, the teaching procedure requires considerable time and effort. Moreover, whenever the relative position between the robot and the object is changed, the operator needs to teach the operation again. To improve the above issue, a strategy that decides the robot motion without the teaching must be developed. This paper proposes a control strategy that does not require teaching and enables the creation of the desired motion without affecting the relative position error between the robot and the target object in object coordinate space defined by a PSD (Position Sensor Detector). In the proposed approach, the estimation algorithm of the kinetic transformation between the global and the object coordinates is introduced by using PSD output, and the error of coordinate transformation estimated by the proposed approach is compensated for in the global coordinate system. The validity of the proposed method is shown using simulations and experiments. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(3): 53–61, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20354

Control of a Handheld Robot for Orthopaedic Surgery

The controller design and implementation of a handheld surgical robot is presented. During the treatment of human bones the robot is able to compensate un-voluntary movements of the surgeon and of the patient and to find automatically the target position of the tool. The robot system is based on a Stewart-platform actuated by linear motors and on an optical tracking system. A cascade controller provides a local position and velocity control of the motor axes and an absolute position control in the world frame. To show the feasibility of the concept, cavities are milled into polystyrene-foam, while the robot is decoupled from the test bed. For clinical demands the robot has to be improved in the static and dynamic accuracy.

SlideBar: Analysis of a linear input device

The SlideBar is a physical linear input device for absolute position control of 1° of freedom, consisting of a physical slider with a graspable knob positioned near or attached to the keyboard. Its range of motion is directly mapped to a one dimensional input widget such as a scrollbar. The SlideBar provides absolute position control in one dimension, is usable in the non-dominant hand in conjunction with a pointing device, and offers constrained passive haptic feedback. These characteristics make the device appropriate for the common class of tasks characterized by one-dimensional input and constrained range of operation. An empirical study of three devices (SlideBar, mouse controlled scrollbar, and mousewheel) shows that for common scrolling tasks, the SlideBar has a significant advantage over a standard mouse controlled scrollbar in user preference. In addition, users tended to prefer it over the mousewheel (without statistical significance).