Features

Where accuracy is concerned, robots have traditionally relied on repeatability. In the past, robotic accuracy has not been developed to a level of maturity acceptable to standard production processes. Critical aerospace manufacturing techniques such as fastening and drilling were historically not held to tight tolerances. Typical tolerances for airframe assembly fastening were in the +0.030" range. The standard is set by the positional requirement for drilling of fastener holes, which is a key target application for robotics in manufacturing.
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Designers of medical pumps often have to deal with the challenge of implementing precise, yet low-cost motion control. For most medical pumps, there are three basic technology alternatives for implementing such electronic motion control: permanent magnet brush DC motors, brushless DC motors, or step motors. Step motors (sometimes called stepping motors, stepper motors, or simply steppers) are a solid choice for position or speed control. Steppers are inherently digital — a pulse applied to the drive electronics results in a shaft movement of one step. They are commonly used “open loop,” meaning without feedback, due to their ability to achieve the desired number of steps every time (if sized properly). The number of incoming pulses and the rate at which they are fed can be used to implement very precise, yet very simple motion (position, speed, and acceleration) control. As long as the speeds required are not too high (less than 3000 RPM, typically), steppers often offer a far simpler, lower-cost, and maintenance- free alternative.
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Fitting the right type of linear position sensor to an application requires at least a working knowledge of the attributes of this electromechanical device. Starting with the basics, the LVDT (linear variable differential transformer) is a common type of linear position sensor widely used in electromechanical systems today. It consists of two basic elements: a stationary coil assembly and a movable core or armature. While most LVDTs are fundamentally AC-in/AC-out devices, some have electronics built-in to make them DC-in/DC-out devices. This gives rise to the terms “AC-LVDTs” and “DC-LVDTs”.
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Axial pumps with cam-driven commutation units — so-called PWK pumps — emerged as a result of a research project conducted in the Department of Hydraulics and Pneumatics at the Gdansk University of Technology. As for all axial hydraulic piston pumps, several cylinder chambers are positioned around the rotating shaft of an axial pump with cam-driven commutation units — called PWK pumps. The rotation of the shaft and the attached swash plate leads to movement of the pistons that alternately decreases and increases the fluid volume of the chambers. A window — which is part of the control sleeve or commutating bushing — connects the chamber between the pistons with the low-pressure and highpressure intake and outtake channels.
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Machine design and deployment requires integration of various technologies such as controls, mechanics, vision, lasers, data acquisition, and software, to mention only a few. These mechatronic solutions usually target a specific purpose such as part manufacturing, marking, packaging, etc. Often the controller is a key focus in the design because it must connect and coordinate all of the processes on the machine. Using separate programmable logic controllers (PLCs) and motion controllers necessitates integration, which is costly and time-consuming. Using a single controller for the machine eliminates the need for integration and shortens design and deployment time and cost.
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Among the various components of a submarine pipeline, the vertical section known as a riser is critical to managing the pipeline. This section connects the piping that runs along the bottom of the sea with the floating production platform.
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Motion control choices are best made in light of the whole system architecture, as the selection of system architecture will drive not only the implementation and integration stages of the project, but also manufacturing and field service, and even the ability to ship and install the final product. We will first review a quick tour of system engineering, and then go on to the motion control specifics.
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