Motion Control

Control Scheme Improves Motor Operation and Interaction

A team of researchers from the Polytechnic University of Bari, Italy, is working to improve how industrial electric drives operate. They propose a new control scheme that will not only improve motor operation, but also how the motor interacts with other systems.

Posted in: News, Motion Control, Motors & Drives, Mathematical/Scientific Software, Simulation Software
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Tool Helps Design Soft Robots That Can Bend and Twist

Designing a soft robot to move organically — to bend like a finger or twist like a wrist — has always been a process of trial and error. Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering have developed a method to automatically design soft actuators based on the desired movement.

Posted in: News, Implants & Prosthetics, Motion Control, Robotics, Computer-Aided Design (CAD), Software
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The Basics of Encoder Selection

Positioning: Resolution and Accuracy

An application’s required positioning resolution dictates the choice of encoder resolution. A well-tuned system can maintain the position within one encoder state (quadcount). Therefore, the encoder resolution in quadcounts (states) should at least correspond to the maximum permissible positioning error. Depending on the response time of the system, a higher encoder resolution should be chosen for the controller to detect deviations faster and counteract quicker.

Posted in: Articles, Motion Control, Calibration, Navigation and guidance systems, Reliability
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How To Substantially Reduce Encoder Cost While Gaining Functionality With Multi-Turn Rotary Position Sensors

Many applications require rotation counters that can measure angles greater than 360º. However the low-cost 10-turn potentiometers most design engineers are familiar with can’t always meet user requirements for resolution and reliability. As an alternative, optical absolute encoders are too expensive for many applications. These solutions require a continuous power supply or they will lose count when power is restored. Also, geared technology/rotation counters are subject to significant wear.

Posted in: White Papers, Motion Control, Automation, Robotics, Data Acquisition, Sensors
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Mechanisms for Achieving Non-Sinusoidal Waveforms on Stirling Engines

The current state-of-the-art Stirling engines use sinusoidal piston and displacer motion to drive the thermodynamic cycle and produce power. Research performed at NASA Glenn has shown that non-sinusoidal waveforms have the potential to increase Stirling engine power density, and could possibly be used to tailor engine performance to the needs of a specific application. However, the state-of-the-art Stirling engine design uses gas springs or planar springs that are very nearly linear, resulting in a system that resonates at a single frequency. This means that imposing non-sinusoidal waveforms, consisting of multiple frequencies, requires large forces from the drive mechanism (either the alternator or the crank shaft). These large forces increase losses, and increase the size and requirements of the control system. This innovation aims to reduce the external forcing requirements by introducing internal mechanical components that provide the forces necessary to achieve the desired waveforms.

Posted in: Briefs, Mechanical Components, Mechanics, Motion Control, Alternators, Crankshafts, Engine efficiency, Stirling engines
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Improving Stirling Engine Performance Through Optimized Piston and Displacer Motion

Stirling engines typically achieve high efficiency, but lack power density. Low power density prevents them from being used in many applications where internal combustion engines are viable competitors, and increases system costs in applications that require Stirling engines. This limits their operating envelope in both terrestrial and space applications. Sinusoidal piston and displacer motion is one of the causes of low power density. Previous work proposed solving this problem by replacing sinusoidal waveforms with waveforms that more closely approximate those of the ideal Stirling cycle. However, when working with real engines, imposing ideal waveforms has been shown to reduce power density and efficiency due to increased pressure drop through the regenerator and heat exchangers.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Motors & Drives, Engine efficiency, Pistons, Stirling engines
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Prototype Capture System Simulates Asteroid Mission

A prototype of the robotic capture module system is tested with a mock asteroid boulder in its clutches at NASA’s Goddard Space Flight Center.

A robotic capture module system prototype was built to help NASA engineers understand the operations required to collect a multi-ton boulder from an asteroid’s surface. The hardware includes three space frame legs with foot pads, and two seven-degrees-of-freedom arms with microspine gripper “hands” to grasp onto the boulder.

Posted in: News, Motion Control, Robotics
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Dike Inspection Robot is Energy-Autonomous

The robot's drive train, including the dual-hemisphere system. (Image: University of Twente)

Inspecting the condition of dikes and other sea defense structures is typically a task for robots, working in a team and in a highly autonomous way. But if they move around across the dikes, perform tests, and communicate the results for six hours a day, they use a lot of energy.

Posted in: News, Motion Control, Motors & Drives, Power Transmission
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System Harvests Energy from Automotive Shock Absorbers

The energy harvesting device focuses on the car’s suspension – specifically, the shock absorbers.

Boosting the fuel efficiency of motor vehicles by “harvesting” the energy generated by their shock absorbers and feeding it back into batteries or electrical systems such as air conditioning has become a major goal in automotive engineering. A University of Huddersfield (UK) researcher has designed a new system and built a prototype that is ready for real-world testing.

Posted in: News, Energy Harvesting, Motion Control
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Pedal Position Sensing in Heavy-Duty Vehicles

Pedal position detection is nothing new when it comes to operation of heavy duty equipment. However, the age old system operation of mechanical linkages between the pedal and the engine just might be coming to an end. New sensor technology is now enabling non-contact, drive-by-wire that can reduce total system cost while standing up to the harsh environments of off highway equipment.

Posted in: White Papers, Fluid Handling, Mechanical Components, Motion Control, Data Acquisition, Sensors
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