Appliance Design - June 2008 - (Page 41)

ELECTRONICS ppliance technology has evolved significantly over the years, and two trends are merging to fuel the next round of appliance evolution — digital motor control and digital sensor processing. Digital Signal Controllers (DSCs) are at the confluence of these trends, and enable digital sensor processing, digital motor control and power factor correction to be implemented on a single chip. DSCs have hardware accommodation for efficient DSP processing on-chip. While many advanced sensorless algorithms do not require DSP, most benefit from on-chip DSP resources. For example, the highly efficient Field-Oriented Motor Control (FOC) algorithm benefits from a single-cycle MAC, accumulator saturation and other features common to DSPs and DSCs, but not typically found on MCUs. While the real world is analog, digital techniques have progressively augmented traditional analog design implementations. At the point where the balance is tipped, where the digital approach cannot be effectively matched with analog wizardry, digital control www.applianceDESIGN.com A and processing become mainstream tools in the designer’s tool bag. Motor control and sensor processing handled by a single chip. Digital motor control The ongoing trend toward electronic control is driving the venerable commutator out of its DC motor shell, as evidenced by the migration from Brushed to Brushless DC (BLDC) motors. Another disruptive shift was the replacement of Hall Effect sensors with resistor dividers to measure EMF feedback, through the main phase connections, to determine rotor position and velocity. Now, advanced algorithms such as FOC are considered highly desirable, due to the resulting excellent torque response, improved motor efficiency and lower audible noise obtained through sinusoidal drives. The FOC algorithm asymptotically decouples the rotor torque and rotor flux, making the speed linearly related to torque current. This permits, for example, an induction motor to possess the same behavior of a separately excited DC motor. All of these motor transformations have one by steve marsh Steve Marsh is strategic marketing manager, Digital Signal Controller Division, Microchip Technology, Chandler, Ariz. applianceDESIGN June 2008 41 http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - June 2008

Appliance Design - June 2008 Contents Editorial Shipments/Forecasts News Watch 21st Annual Excellence in Design Winning Designs Combine State-of-the-art Technology with . . . Meet the Judges Design Marts Fans & Blowers Mother Nature Has Her Own Ideas About Designing for Fluid Flow . . . Using CFD Simulation Software Early in the Product Development . . . Electronics Digital Signal Controllers Enable Digital Motor Control . . . Classifieds Meetings Advertiser’s Index Association Report: AHRI

Appliance Design - June 2008

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