Market drivers and solutions
Electronic motor control requirements in home electronics, the industrial and automotive markets have driven the need for MCUs with advanced motor control peripherals.
In the home appliance market, motor control with improved performance is needed to meet government planning standards, such as the Energy Star Program of the US Environmental Protection Agency, which promotes the introduction of high-performance appliances. Washing machines are an important area of high performance motor control. The direct drive washing machine eliminates the drive belt between the motor shaft and the washer agitator, allowing for different speed and agitator modes.
A manufacturer's fully redesigned washing machine consumes 38% less electricity and 17% more water than a conventional washing machine. The motor control MCU adjusts the power of the motor according to the amount and type of laundry. However, home appliance users are still sensitive to the initial purchase price, so manufacturers must continuously reduce their development and production costs so that more advanced appliances can be accepted by more consumers.
In home appliances, 8-bit MCUs designed specifically for low-cost motor control applications integrate features that minimize additional components. With motor PWM on the board, fail-safe clock monitor and highly reliable flash memory, the latest MCUs simplify the design of home appliance motor control and achieve low cost targets.
In industrial applications, power costs and downtime of assembly operations can reduce the benefits of the manufacturer. An industrial example of how control of motor performance improvements directly affects efficiency and profitability is to replace a valve in an industrial pump with a variable speed (VSD) system with an MCU.
For a pump or fan, the power consumption is proportional to the cube speed of the shaft. When the shaft speed is reduced by 10%, the flow is reduced by 10% and the power consumption is reduced by 27%. If the speed is reduced by 20%, the power consumption is reduced by 49%. By using MCU variable speed motor control instead of constant speed motor valves to reduce flow, it has been proven that 25-40% energy savings can be achieved for centrifugal pumps, fans and blowers in industrial applications.
The benefits of industrial applications are obvious, and MCU-driven variable speed motor control relies on other factors such as flexibility and reliability - these factors can avoid downtime caused by faults or overhauls. MCUs with flash and EEPROM provide the flexibility to solve industrial user requirements with reprogrammable features when upgrades or control program requirements are required. An MCU with 16KB of flash memory and 256BEEPROM provides enough memory in an 8-bit MCU to handle many of the changes that may be required in an industrial environment. Equally important, Microchip's flash memory uses PMOS electronically erasable unit processing technology that typically has a data storage unit capable of withstanding 1 million erase/write cycles and data that can last for more than 40 years.
Existing automotive motor applications include the use of motors to open and close windows and doors, and to position the seats. Because these applications are used at a low frequency, they are not sensitive to inefficiencies, but high-utilization applications, such as passenger temperature environment control and engine box fans, continue to consume limited power from the car. The motor control MCU allows the environmental control fan to operate at a speed that maintains a comfortable temperature, thus minimizing noise and reducing power consumption.
In many cases, the motor control MCU must be connected to the car network using a Control Area Network (CAN) or a Local Interconnect Network (LAN). For body electronics, low-cost LIN protocols are now used to reduce overall system cost. In some MCU families, a USART module supporting LIN 1.2 can be found, along with automatic wake-up and baud detection at the start bit.
As control algorithms become more complex in all market segments, the performance of digital motor controllers rises from the MCU to the DSP level. Digital Signal Controllers (DSCs) bring higher performance and affordable, design engineer-friendly MCU technology for more sophisticated motor control designs, including those with vector control. DSCs operate at speeds up to 30 MIPS, with integrated peripherals dedicated to flash memory and motor control up to 144 KB for more advanced, new motor control applications. With electronic motor control based on DSP and DSC, home appliance industry control and automotive not only work more efficiently, provide more functions, and are more affordable.
