Stepper

Abstract: The design concept of a spherical stepper motor capable of three-degrees-of-freedom (DOF) motion in a single joint is presented. The ball-joint-like motor has no singularities except at the boundary of the workspace and can perform isotropic manipulation in all three directions. Due to its relatively simple ball-like structure, undesired cross-coupling and centrifugal components of wrist rotor dynamics can be effectively minimized or eliminated. The spherical stepper motor has potential in robotic applications as a three-DOF shoulder or an eyeball, as well as a wrist actuator. In particular, the systematic conceptualization of a spherical stepper is presented, and the feasibility of constructing the spherical stepper is examined. Along with the experimental data, an analytical approach based on the permeance formula was used to predict the driving forces generated by a neodymium-iron permanent magnet. The force-displacement curves provide useful information for rational spherical motor design and control. >

Abstract: 1 Introduction.- 2 Dual-Axis Linear Stepper (Sawyer) Motors.- 3 Modeling of Stepper Motors.- 4 Stepping.- 5 Feedback Linearization and Application to Electric Motors.- 6 Robust Adaptive Control of a Class of Nonlinear Systems.- 7 Robust Adaptive Control of Stepper Motors.- 8 Current Control of Stepper Motors Using Position Measurements Only.- 9 Voltage Control of Stepper Motors Using Position and VelocityMeasurements.- 10 Voltage Control of PM Stepper Motors Using Position Measurement Only.- 11 Brushless DC Motors.- 12 Induction Motor: Modeling and Control.- 13 Adaptive Control of Induction Motors.- 14 Passivity-Based Control of Electric Motors.- 15 Torque Ripple Reduction for Step Motors.- 16 Friction Compensation in Servo-Drives.- A Fundamentals of AC Machines.- B.1 Case of Position-Only Dependent Transformations.- C Torque Maximization with Current and Voltage Constraints (Field Weakening).- C.1 Low-Speed Range.- C.2 High-Speed Range.- C.3 Intermediate-Speed Range.- C.4 Transition Speeds.- D Stable System Inversion.- E Lyapunov Stability Theorems.- F Backstepping.- G Input-to-State Stability and Nonlinear Small Gain.

Abstract: Varifocal lenses are essential components of dynamic optical systems with applications in photography, mixed reality, and microscopy. Metasurface optics has strong potential for creating tunable flat optics. Existing tunable metalenses, however, typically require microelectromechanical actuators, which cannot be scaled to large area devices, or rely on high voltages to stretch a flexible substrate and achieve a sufficient tuning range. Here, we build a 1 cm aperture varifocal metalens system at 1550 nm wavelength inspired by an Alvarez lens, fabricated using high-throughput stepper photolithography. We demonstrate a nonlinear change in focal length by minimally actuating two cubic phase metasurfaces laterally, with focusing efficiency as high as 57% and a wide focal length change of more than 6 cm (>200%). We also test a lens design at visible wavelength and conduct varifocal zoom imaging with a demonstrated 4× zoom capability without any other optical elements in the imaging path.

Abstract: This article discusses the transition of a form of nanoimprint lithography technology, known as Jet and Flash Imprint Lithography (J-FIL), from research to a commercial fabrication infrastructure for leading-edge semiconductor integrated circuits (ICs) Leading-edge semiconductor lithography has some of the most aggressive technology requirements, and has been a key driver in the 50-year history of semiconductor scaling Introducing a new, disruptive capability into this arena is therefore a case study in a "high-risk-high-reward" opportunity This article first discusses relevant literature in nanopatterning including advanced lithography options that have been explored by the IC fabrication industry, novel research ideas being explored, and literature in nanoimprint lithography The article then focuses on the J-FIL process, and the interdisciplinary nature of risk, involving nanoscale precision systems, mechanics, materials, material delivery systems, contamination control, and process engineering Next, the article discusses the strategic decisions that were made in the early phases of the project including: (i) choosing a step and repeat process approach; (ii) identifying the first target IC market for J-FIL; (iii) defining the product scope and the appropriate collaborations to share the risk-reward landscape; and (iv) properly leveraging existing infrastructure, including minimizing disruption to the widely accepted practices in photolithography Finally, the paper discusses the commercial J-FIL stepper system and associated infrastructure, and the resulting advances in the key lithographic process metrics such as critical dimension control, overlay, throughput, process defects, and electrical yield over the past 5 years This article concludes with the current state of the art in J-FIL technology for IC fabrication, including description of the high volume manufacturing stepper tools created for advanced memory manufacturing