New Motion Control Architecture Simplifies Washing Machine Motor Control System Development

This paper describes a new variable speed motion control system for washing machine applications. The system targets permanent magnet synchronous motors that are now being adopted by appliance manufacturers. Instead of using shaft position sensors, such as Hall devices, a sensorless algorithm estimate rotor angle based on measured stator currents and the applied voltages. The stator currents are measured by sampling currents in the dc link shunt. A field oriented control algorithm allows good dynamic control of torque, which eases load balancing. Field weakening control allows a wide speed range along with additional functions to optimize torque output from interior permanent magnet (IPM) motors. The digital control algorithm is implemented using a unique hardware engine that allows algorithms to be designed using graphical tools. A new digital control IC integrates the hardware control engine, analog circuits for feedback sampling and an 8 bit microcontroller for the appliance application software. An inverter power module that includes a gate drive IC with washer specific safety features completes the solution