Motion Control

Moving Magnet Voice Coil Actuators Offer Controllable Movement for High-Duty-Cycle Applications

There are two types of voice coil actuators: moving coil and moving magnet. The materials of construction are similar, since they both use rare earth magnets, steel, copper wire, and basic insulation materials. There is a tendency to want to say one type is better suited for certain applications; however, there are many different sizes and shapes of voice coil actuators, making it difficult to make blanket statements about which type of actuator works better, and where.

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Optimizing Closed-Loop Control in Hydraulic Motion

Performing closed-loop control of hydraulic servo systems is often more challenging than controlling servomotor systems. The main reason is that hydraulic systems use compressible oil to move the actuator. Because of this, a hydraulic system can be modeled as a mass between two springs, where the piston and the load is the mass, and the oil on both sides of the piston represents the two springs. In contrast, servomotor systems are easier to control because there is basically only the inertia of the motor and the connected load to be dealt with.

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Robotic Exoskeleton Vastly Improves Quality of Life

Worldwide an estimated 185 million people use a wheelchair daily. A company based in Auckland, New Zealand, has developed an innovative robotic technology that helps people with mobility impairment get back on their feet— the Rex Bionics robotic exoskeleton. Its integrated maxon motors help to ensure smooth limb movement.

Posted in: Rehabilitation & Physical Therapy, Implants & Prosthetics, Biosensors, Mechanical Components, Power Supplies, Electronics, Power Management, Manufacturing & Prototyping, Motion Control, Motors & Drives, Power Transmission, Positioning Equipment, Medical, Orthopedics, Articles, Features, MDB

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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.

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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.

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Gearboxes

The i-series planetary gearboxes from Groschopp (Sioux Center, IA) are available with AC, PMDC, and brushless motors, and are made of cast aluminum. They are offered with up to three stages of steel cut or optional plastic gears, suitable for both leftand right-hand rotation running, in continuous and intermittent duty operation. The plastic gears can withstand operating temperatures from -15 to 65 °C; the steel gearing can withstand -30 to 140 °C temperatures. Rated at a standard IP54, the gearboxes feature sealed, doubleball output bearings and gaskets between each module to resist grease and dust.

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Machine Design Software

CD-adapco (Melville, NY) offers two connected simulation programs, SPEED and STAR-CCM+, for machine design. The SPEED tool is used to design motors, generators, and alternators; STAR-CCM+ is a heat transfer and thermal fluid flow program. Design data is seamlessly transferred between the two programs. The SPEED model is created and solved with static/dynamic analytical analysis. SPEED FE is used to fine-tune the analytical model and calculate the iron losses. The 3D machine geometry is set up in STAR-CCM+, including the end windings creation from SPEED via an xGDF file. Flow heat loss results are transferred from FE analysis to STAR-CCM+ via the SBD-file, and heat losses are mapped automatically. The cooling system, bearing shields, and additional flanges are added via importing from a 3D CAD system. Physics are assigned, and the final solution and post-processing are done in STAR-CCM+.

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