Reduce operating time to one-tenth of the CPU software configuration while ensuring functional safety
Tokyo, Japan, February 7, 2017 - Renesas Electronics Corporation (hereinafter referred to as "Renesas Electronics", TSE: 6723), a leading global semiconductor solutions provider, today announced the successful development of a dedicated circuit for motor control. Technology can help car manufacturers meet more stringent carbon emission standards.
The newly developed technology, called the Intelligent Motor Timer System (IMTS), is a dedicated circuit module that can be integrated into future electric and hybrid vehicle microcontrollers. For field-oriented control (FOC), which is critical in electric motor motor control (Note 1), its operating time is only 0.8 microseconds (μs), which is the fastest rate in the world (Note 2). One-tenth of the software processing time on a CPU running at the same operating frequency. This will help develop high-speed electric motor motors with excellent energy efficiency and inverter systems with high-speed switching performance.
In addition, this unique circuit provides functional safety support for automotive power systems.
In recent years, as fuel efficiency requirements have increased, the share of electric vehicles, hybrid vehicles, and plug-in hybrid vehicles in the automotive market has gradually increased. In order to further improve the application range of electric vehicles, it is necessary to enhance the energy efficiency of motor control.
Therefore, it is important not only to mechanically improve the motor, but also to improve the function and performance of the motor's electronic control unit. The electronic control unit that can be used to support the next generation of electric, hybrid and plug-in hybrids requires very advanced features and sophisticated control software, which will inevitably increase the processing of microcontrollers in these electronic control units. load. At the same time, in order to ensure high reliability in a high temperature environment, it is also necessary to limit the amount of heat generated by the automotive microcontroller. Therefore, it is necessary to keep the operating frequency of the microcontroller's internal circuits (including the CPU core) at a relatively low level, which hinders its performance improvement.
In order to meet the above requirements, Renesas Electronics uses IMTS as a dedicated circuit module for static processing in the numerous motor control performed by the microcontroller, because the process usually requires high response performance, such as collecting sensor data, and calculating on this basis. Output control values, etc. Independent of the CPU, IMTS operates autonomously and significantly reduces the CPU load on the motor control microcontroller. The saved CPU performance can be distributed to advanced motor control algorithms to increase the energy efficiency of future electric, hybrid and plug-in hybrids.
Key features of dedicated motor control circuit technology: (1) Development of dedicated circuit modules for static motor control processing and circuit technology supporting independent operationMotor control requires a series of static processing involving field oriented control (FOC). During each control cycle, the MCU will collect the motor current value and angle value to calculate the control value of the next cycle after calculation; on the basis of the control value Generate PWM output (Note 3). When multiple motor control programs are running simultaneously, the total processing load generated by Renesas Electronics' 40nm automotive MCU operating at 320 MHz can account for up to 90% of its CPU (Note 4) performance. The newly developed IMTS is a dedicated circuit module that supports FOC operation, which can largely share the processing load of the CPU. It is configured in the form of a dedicated motor control timer circuit with a compact link, so a series of processing performed during the control cycle managed by each timer circuit—from taking current and angle values ​​to PWM signal output—can be independent of the CPU run.
This eliminates the load that would otherwise have been handled by the CPU, and the released CPU performance can now be distributed to software containing advanced control algorithms to improve energy efficiency. By configuring a dedicated circuit for the FOC, IMTS can reduce the operating processing time to 0.8 μs, which is less than one-tenth the time compared to software configured on the CPU. For power supplies made with new materials, the new technology delivers processing performance that meets inverter control requirements with high-speed switching performance (performance example: 100 kHz switching frequency, control period 10 μs), including new uses such as silicon carbide Inverter for power supply equipment made of materials.
Automotive powertrain control must ensure functional safety in order to detect component failures in a timely manner and automatically transition the system to a safe state. This is typically achieved by using two microcontrollers to provide system redundancy, or an MCU with internal redundant circuitry, but the cost of the latter is relatively high.
The new technology uses an MCU with two dual-core lock-step configurations that periodically monitor the internal operation of the IMTS circuit. This method not only reduces costs, but also achieves high-speed control and functional safety. Functional safety increases the CPU load, but in actual use, it only accounts for 2.4% of the total CPU processing power (Note 5).
(3) Circuit technology can flexibly correct external sensor signal errorIn order to achieve accurate processing performance of high-precision microcontrollers, it is necessary to acquire high-precision sensor signal values. However, in actual operation, there are errors caused by various reasons, such as errors caused by the installation position of the sensor. The newly developed IMTS can load user-developed software real-time correction errors. In addition, IMTS can perform this correction process independently without incurring additional load on the CPU. The correct sensor signal value enables more accurate processing performance and higher energy efficiency in motor operation.
Renesas Electronics is currently testing a 40nm MCU prototype (with on-chip flash) using this technology. It uses a real motor drive system to confirm operation in real systems. Renesas Electronics aims to achieve higher energy efficiency for electronic control units for electric vehicles, hybrid vehicles and plug-in hybrid vehicles through this dedicated motor control circuit technology.
At the 2017 International Solid State Circuits Conference (ISSCC 2017), held on February 5, 2017 (February 6, local time) in Los Angeles, California, Renesas Electronics published a paper on new technologies.
(Note 1) Field Oriented Control (FOC) is a basic processing algorithm widely used in motor control. This motor control algorithm usually uses complex calculations, including trigonometric functions, for coordinate transformation to generate closer to the specified control value. DC signal.
(Note 2) February 7, 2017, based on research by Renesas Electronics.
(Note 3) PWM stands for pulse width modulation, which is used to drive an external power device using an MCU.
(Note 4) It is expected that the next generation system will require a control cycle of 12.5 μs. The calculated value of the CPU load is based on the simultaneous occurrence of two motor control operations (for example, the drive motors of the front and rear wheels) in each control cycle.
(Note 5) The calculated value of the CPU load assumes that the motor detects a failure during the duration of one rotation when it is running at 100,000 rpm.
About Renesas Electronics Co., Ltd.Renesas Electronics Corporation (TSE: 6723) provides customers with professional and trusted innovative embedded designs and complete semiconductor solutions designed to safely and reliably improve people's work and use billions of connected smart devices using their products. lifestyle. As the world's leading supplier of microcontrollers, analog power devices and SoC products, Renesas Electronics offers a wide range of applications for automotive, industrial, automotive (HE), office automation (OA), and information and communication technologies (ICT). Professional technical support, quality assurance and comprehensive solutions, look forward to working with you to create an infinite future. For more information, please visit renesas.com.
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