Motion Control

Feedback Sensors Keep Servomotors on Target

Fundamentally, a servo system can perform no more accurately than the accuracy of the feedback device controlling it. In addition, errors in speed or position can be introduced into the system by the less-than-perfect mechanisms that transfer the motor power to the load. Environmental factors like electrical noise or temperature may also introduce positioning errors. Sometimes the errors are acceptable. More frequently, however, they are not. When it comes to high-performance servo applications, feedback devices fall into several different categories. Each offers unique advantages and disadvantages, both electrical and mechanical, that make one better suited for a particular application than another.

Posted in: Articles, Motion Control, Failure analysis, Sensors and actuators, Noise, Auxiliary power units

Handling Delicate Materials

Special care needs to be taken when handling delicate materials used in medical applications. Small diameters provide increased flexibility needed for long-flex-life applications such as cardiac catheter wires. Many other applications also use these fine materials as winding and braiding materials, including the medical device industry, microelectronics, and composites.

Posted in: Articles, Motion Control, Microelectromechanical devices, Medical equipment and supplies, Materials handling, Fibers

Real-Time Software Enables Multi-Core PCs for Industrial Automation

As early as 25 years ago, industrial system integrators saw the great potential that the Windows operating system brought to PCs. They saw the possibility of using the advanced graphic capabilities that Windows offered versus the relatively primitive human interfaces of DOS-based applications and those of other proprietary OSes. Windows enabled the development of controllers with advanced human-ma chine interfaces (HMIs) that provide a whole new level of functionality, and make machines easier to use and maintain.

Posted in: Articles, Motion Control, Computer software and hardware, Human machine interface (HMI), Automation, Industrial vehicles and equipment

Using Source Measure Units to Characterize High-Power Semiconductors (Part 1)

The proliferation of electronic control and electronic power conversion into a variety of industries (e.g., energy generation, industrial motor drives and control, transportation, and IT) has made efficient power semiconductor device design and test more critical than ever. To demonstrate technology improvements, new device capabilities must be compared with those of existing devices. The use of semiconductor materials other than silicon demands the use of new processes. To be sustainable, these new processes must be tuned to deliver consistent results and high production yield. As new device designs are developed, reliability measurements must be performed on many devices over long periods. Therefore, test engineers must identify test equipment that is not only accurate, but scalable and cost-effective.

Posted in: Articles, Motion Control, Semiconductor devices, Test equipment and instrumentation, Test procedures

Linear Guide Systems Streamline Aircraft Seat Assembly and Operation

Linear guide rails are an important component within aircraft interiors. Following are some of the places where they are used:

• For seat adjustments — forward and back seat movements, footrests, sliding armrests, and tables. • Rails enable 180° positioning for super first class seats that flatten for sleeping. • Sliding privacy screens between passengers. • Kitchen slide-outs, such as garbage compactors. • Sliding lavatory doors.

Posted in: Articles, Motion Control, Seats and seating, Assembling, Aircraft

Robotic Accuracy Improves Aerospace Manufacturing

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.

Posted in: Articles, Motion Control, Drilling, Fastening, Robotics, Quality standards

Hybrid Stepper Advancements Improve Medical Pump Performance

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.

Posted in: Articles, Motion Control, Hybrid power, Medical equipment and supplies, Pumps, Electric motors

Factors to Consider When Selecting and Specifying LVDT Linear Position Sensors

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”.

Posted in: Articles, Motion Control, Architecture, Microelectromechanical devices, Sensors and actuators

Simulation of Fluid-Structure Interaction in Hydraulic Pump Design

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.

Posted in: Articles, Motion Control, Computational fluid dynamics, Pumps, Cams, Hydraulic equipment, Pistons

Reducing Machine Controller Design and Deployment

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.

Posted in: Articles, Motion Control, Computer software and hardware, Automation

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