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Sneak Peek: Motors and Motion Control

Originally Published MPMN October 2005

Product Update

Sneak Peek: Motors and Motion Control

The need for motors and motion control products is escalating rapidly as a stream of burgeoning technologies, robots, and devices flood the market. And with these advancements and changes inevitably come a multitude of industry trends.

As is true in many areas of the medical manufacturing industry, the move towards miniaturization is affecting the field of motion control. The mounting popularity of minimally invasive surgery requires reducing the size of necessary components. In addition to the shrinking size of motion control products, there is also a demand for smaller machinery, as cumbersome equipment occupies valuable facility space. Finally, there remains the ongoing quest for smart motion control products that require minimal supervision and maintenance, but retain user-friendly features.

A Piezoelectric Actuator Provides Precision Positioning

A company specializing in precision motion control offers a piezoelectric actuator suited for applications such as miniature valves, optical switching and scanning, and nanopositioning. The titanium FPA-125 piezo actuator made by Dynamic Structures and Materials LLC (Franklin, TN) measures 7.6 × 7.6 × 25.4 mm and weighs 6 g.

The actuator offers a variety of features in addition to its compact size. The unit is mechanically preloaded to guarantee bidirectional operation. This feature provides increased resilience to mechanical loads when compared with nonpreloaded actuators, according to the company. Although varying piezo materials and voltages are available upon request, the standard model is equipped with low-voltage piezo material ranging from 120 to 150 V. The actuator has a stroke of 125 µm to ±10%, a stiffness of 1 N/µm to ±10%, and an unloaded resonant frequency of 1400 Hz to ±5%. The flexure-based actuator is also comprised of cleanroom- and vaccum environment–compatible materials.

Stepper Drive Features Special Functions to Avoid Common Motor Problems

Featuring a comprehensive set of specialized functions, a stepper drive curtails common stepper motor transgressions. Applied Motion Products (Watsonville, CA) offers the STAC6. The drive combines an output current of 0.5–6 A with an ac input of 94–135 V. It operates in a temperature range of 0–55°C.

The STAC6 is equipped with a bevy of special functions aimed at circumventing common problems associated with step motors. To maintain smooth motion while using low step resolutions, the drive has a microstep emulation feature that converts the step count into microsteps, which are then fed to the motor. A demand signal smoothing function diminishes the effect of abrupt changes in velocity and direction, while a negative harmonic negates inherent low-speed torque ripple, resulting in a smoother motion at low speed. Users can also input system data in order to calculate the frequency at which the motor resonates. The antiresonance function will then enter a dampening term into the algorithm to improve midrange stability, allowing stable operations to 50 rps or greater.

In conjunction with the various preventative functions, a self-test feature works to eliminate glitches and to avoid common actions that may hamper the production process. The self-test function measures the motor’s parameters at the startup stage and compares the information from the previous startup in order to check for data changes that may indicate a problem or alteration. More functions are available with the addition of an encoder. The drive detects and prevents stalls, as well as maintains motor position when stopped, despite external forces.

A Motor Controller Is Suited for Hand-Held Surgical Drills

A motor controller that measures 1.25 × 3 in. serves as a handheld tool for brushless drills. The autoclavable, variable-speed motor controller is designed by Sensitron Semiconductor (Deer Park, NY) to withstand 10,000 autoclave cycles. Outfitted with an overtemperature shutdown protection function, the controller automatically ceases operations when the product temperature climbs too high. An automatic restart function then activates the power once the temperature has returned to a safe value. The product also has a low current sense resistor value with high-temperature gain. Operating temperature ranges from –50° to 125°C. The controller meets UL 2601-1, CSA 601, and IEC 60601-1 standards.

Linear Servo Amplifiers Feature Low-Noise Performance

A motion control product manufacturer has introduced a 500-W version to its line of transconductance linear servo amplifiers that reportedly eliminate the radiated noise and distortion typically found in pulse-width-modulated servo amplifiers. Varedan Technologies (Torrance, CA) offers servo amplifiers in 200-, 400-, and 500-W versions with high bandwidth. The amplifiers are suited for applications such as linear air bearing stages, rotary air bearing spindles, ultrasonic scanning, coordinate measurement machines, disk inspection spin stands, and thermoelectric cooling control. Other applications include fiber-optic welding, high-resolution positioning systems, semiconductor processing equipment, and linear and rotary servo stages.

The amplifiers incorporate user-friendly features, including an onboard DSP that monitors real-time status, a function that stores parameters in a nonvolatile memory, and an autobalance capability that enables full power to be delivered to the windings of the motor without manual equalization of the amplifiers. With motor-mounting Hall sensors, the amplifiers can drive brushless motors in either sine or trapezoidal mode.

Shana Leonard



Copyright ©2005 Medical Product Manufacturing News

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