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Sensorless control platform target washing machines

Posted: 02 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:International Rectifier? IR? sensorless control? direct-drive? PMSM?

International Rectifier (IR) has introduced a sensorless control platform for direct-drive permanent magnet synchronous motor washing machines. IR said the new platform, featuring an embedded field oriented control (FOC) algorithm for high-dynamic torque control, improving washing cycles and consuming less hot water to save up to 70 percent of energy usage.

The latest addition to IR's iMOTION family features a mixed-signal controller and companion intelligent power modules as well as algorithms, development software and design tools. Combined in one platform, iMOTION for washers simplifies design of variable-speed motor-control in both horizontal and vertical axis washing machines, accelerating time-to-market and reducing overall system cost, said the company.

"Typically, Hall Effect sensors are deployed to provide rotor position information necessary for control of [PMS] motors, adding cost and complexity to the motor design. The iMOTION platform enables sensorless sinusoidal current control, completely eliminating Hall Effect sensors and delivering smooth torque over an extended speed range," said David Tam, vice president of the company's energy-saving products segment.

Mixed signal control
IR said the IRMCF341 washer control IC integrates all the control and analog interface functions required for sensorless speed control of PMS motors using DC link current measurements. The analog functions on the IC include differential amplifier, dual sample and hold circuits and a 12bit A/D converter to sample the low-voltage signal across the DC link shunt. The digital control IC features IR's patented Motion Control Engine (MCE) that eliminates software coding from the motion control algorithm development process, the company said.

A co-integrated 60MIPS, 8bit, 8051 microcontroller enables application layer software development, operating almost independently of the MCE and does not compete for system resources such as interrupts or internal registers. This streamlines application software debugging since the MCE can be treated very much like hardware peripheral with a set of input and output registers, said IR. The embedded analog signal engine integrates all the signal conditioning and conversion circuits required for single current shunt, sensorless control of a PMS motor. The new control IC is available in a 64-pin QFP package with all the required analog inputs and PWM outputs to control the washing machine motor.

The companion IRAMS06UP60B and IRAMS10UP60B inverter power modules feature an advanced high-voltage gate drive IC for three-phase inverter control. The modules include the DC link shunt used for both motor current measurement and power module protection. Built-in over-temperature/over-current protection, along with short-circuit rated IGBTs, an integrated under-voltage lockout function, and built-in temperature monitor provide a high level of protection and fail-safe operation, said IR.

Design tools
The platform includes the IRMCS3041 reference design, in addition to web-based software tools, to customize application requirements. IR said the embedded FOC algorithm optimizes the output torque from interior permanent magnet motors and maximizes bus voltage utilization in the high-speed field weakening mode.

Tools include communications software running on the 8051 microcontroller that gives the PC-based MCEDesigner software access to the control parameters and system variables in the shared memory. This allows modification of the controller set points and control loop gains and other constants without needing to modify or compile software, said IR. MCEDesigner tools generate wash-cycle profiles and plot motor speed and current, accelerating rapid evaluation of direct-drive motor performance with real washing loads.

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