Part 2 ― The Renesas Approach to Motor Control

Basic Strategy Aims to Provide Design Solutions for a Wide Span of New and Evolving Applications

With an increasing number of applications requiring highly precise control of electric motors at low cost, Renesas is strengthening our range of microcomputers to meet motor control requirements in diverse fields ranging from factory automation (FA) to home appliances and other consumer products. To get an overview of Renesas' involvement in motor control and our basic business strategy for this multifaceted application area, EDGE spoke with Terukazu Watanabe from the Microcomputer Product Engineering Division of the Microcomputer Business Unit. His comments highlighted not only the great depth and breadth of the solutions available now, but also some of the work being done to meet future market needs.

Motors don't just need to run, they also require control circuitry optimized for the systems they are used in and must offer features such as energy efficiency and quiet, maintenance-free operation. Motor control electronics solutions have to meet the specific requirements of the type of motor being controlled, whether it's a brushless DC motor, a high-performance industrial AC motor, or one of many other types. As a result, the microcomputers used in motor control applications have to provide a broad span of performance levels and offer many different on-chip functions with diverse features and capabilities. "Renesas has responded to these demands with an extensive product range, with computing performance from several MIPS to several hundred MIPS and with feature sets optimized for specific applications. We can satisfy all motor control microcomputer needs, from low-end to high-end," Mr. Watanabe said.

At the low end, the Renesas motor control solutions are based on R8C/Tiny series devices that target consumer products. Our mid-range solutions are based on chips in the M16C family and target home appliances, among many other products that use electric motors. At the high-end, our solutions for precision factory automation applications use SuperH? processors to achieve the required high processing throughput. Referring to this three-tiered span of solutions, which is depicted in Figure 1, Mr. Watanabe pointed out that "the mid-range models cover a wide area ― the heart of the market." He then added, "To facilitate future motor control upgrades in this area, we are developing new CPU cores that will inherit the DNA of the H8, H8S, and M16C series chips and offer upward compatibility with the existing devices." ( Click here for related story. )

Motor control is real-time control and this specialized area of embedded system technology is being pushed to new limits in high-end applications. "Our SuperH based solutions are the flagships of the Renesas motor control microcomputer range. They have high-performance SH-2 or SH-2A 32-bit RISC CPU cores that deliver processing performance of up to 480MIPS. These devices allow our customers to build highly advanced motor control systems for industrial applications such as precision metal machining equipment. To offer even better performance, we have introduced an advanced microcomputer that integrates two SH-2A cores. It achieves a maximum performance of 960MIPS and was described in volume 17 of the EDGE magazine," Mr. Watanabe said.

Renesas is working actively to enhance the motor control timer, A/D converter, floating point unit (FPU), networking, internal memory, and other on-chip peripheral functions in its lineup of microcomputers for motor control applications. Here are some highlights:
・All of the general-purpose microcomputers in the R8C/Tiny series of 20-pin to 80-pin devices provide an internal multifunction timer and therefore are capable of controlling brushless DC motors.
・Devices in the M16C/Tiny series offer a timer unit inherited from the higher-specified M16C series that can be used to control three-phase AC and PMSM motors.
・Among the built-in functions useful for advanced motor control applications that SuperH series microcomputers provide are the FPU in the SH7203 group (which uses the SH-2A core), and the A/D converter in the SH7211 group (see Figure 2).

Devices in the SH7211 group operate at 160MHz and have 512Kbytes of internal flash memory. Commenting on this, Mr. Watanabe noted that "motors tend to generate a lot of electrical noise, so there is a strong demand to use single-chip solutions wherever and whenever possible. This is one of the factors driving engineers' requests for more internal flash memory."

The Renesas microcomputers used for controlling electric motors may have some specialized functions, but nevertheless they are general-purpose devices. Thus, they can be used for other system control functions, too. Therefore, the devices offer benefits in terms of both miniaturization and cost reduction. "Renesas has embarked on a strategy of providing increased added-value in our microcomputers. We already have plans to incorporate functions such as CAN network support and LCD controllers into future chips," Mr. Watanabe revealed.

We are also working on research into motor control technology itself. Initiatives underway include algorithm development contracted to the research laboratories of Renesas' parent companies, Hitachi and Mitsubishi Electric. One result of this research is the early commercialization of a single-shunt control function for three-phase motors.

To help customers adopt the latest motor control technology for improving the performance of their products, we have created a starter kit for the application. "The kit acts as an introduction to motor control and makes it easy ― even for beginners ― to try out the operation of motor control microcomputers," Mr. Watanabe explained.

The three sections that follow in Part 3 of this Special Feature look at Renesas motor control solutions for applications in factory automation, home appliances, and consumer products. The main stories in each section describe appropriate devices and support products, while sidebars summarize key microcomputers recommended for new designs. Case studies are also presented that highlight the experiences of customers that are using our motor control solutions in their products.