Implementing servo motor control with high-performance MCUs and MPUs removes the need for an FPGA or ASIC and improves the speed and precision of industrial robots and machine tools in factories.
The RZ/T1 is a highly integrated device that includes dedicated peripherals for real-time Ethernet communication, encoder interfaces, and delta-sigma current sensor interfaces that allows for advances in the development of high-performance servo drive control technology. Part 3 includes discussion from industry users who provided feedback from the front lines of research and development (R&D).
The Possibilities of RZ/T1 as Seen by Authorities on Servo Motor Control
In the first and second articles, we looked at what kind of changes are taking place on the front lines of factory automation (FA) heading into the age of the Internet of Things (IoT) and machine-to-machine (M2M) communications, particularly as related to servo motor control. In Part 3, we talk to Professor Yen-Shin Lai of National Taipei University of Technology, which is promoting cutting-edge research in the field of motor control, and the R&D manager of Germany-based Company K, a manufacturer of FA equipment, as industry leaders facing these changes. They offer real feedback from the front lines of R&D, having actually used the RZ/T series from Renesas Electronics.
RZ/T1: Essential for Cutting-Edge Research on Servo Motors
Interview with Professor Yen-Shin Lai of National Taipei University of Technology
May we first ask about what do you and your team study?
Over the past 20 years, our main themes of study in FA related fields are vibration suppression and control of servo drives, specifically PWM control for AC drives, BLDC motor drives with/without Hall sensors, field weakening control for induction motor drives, and MTPA*1 and MTPV*2 control for both SMPMSM*3 and IPMSM*4.
Would you please share in detail about your research & development on what system with RZ/T1? Also, may we ask how does RZ/T1 fit into your system?
Our current research involves design and implementation of high bandwidth servo drives using a 750W SMPMSM with 17-bit absolute encoder. All control including, current, speed and position loops, are made possible with RZ/T1. The goal of our developed servo drives includes investigation of high bandwidth controllers. The special features of RZ/T1, including floating point operation, 600MHz of clock for CPU, and fast AD conversion time and high resolution PWM generation, help us to achieve dual sampling per switching cycle and calculation of current loop control in 8µs. And our test results show the following results can be achieved using only a 32-bit ARM®Cortex®-R4 Processor with FPU of RZ/T1.
- For 10kHz switching frequency, 1.5kHz and 200Hz of bandwidth for current and speed loop, respectively.
- For 20kHz switching frequency, 2.6kHz of bandwidth for current loop (speed loop bandwidth is still under test).
*1 Maximum Torque Per Ampere
*2 Maximum Torque Per Voltage
*3 Surface Mounted Permanent Magnet Synchronous Motor
*4 Interior Permanent Magnet Synchronous Motor
Benefits of Having a High Bandwidth Controller
Control loops can be made at a high band (in a short period), so a servo can be operated at higher speed and with higher precision. When a servo can be quickly and precisely turned to a specified position (it is ideal if it stops exactly without overshooting), it has the benefit of improving the productive efficiency of for example an industrial robot by leaps and bounds.
By actually using RZ/T1, would you please share your view of how better RZ/T1 is?
After using the RZ/T1 in our development of servo drives, some superb points of its performance should be highlighted.
- Floating point CPU with maximum operating frequency of 600MHz shortens the calculation time and its related delay.
- SAR ADC module with 60MHz clock and 12-bit resolution (ADC conversion time 600ns) reduces the sampling delay.
- Using a multi-protocol encoder interface hardware approach reduces the CPU load required for encoder data processing.
How do you think RZ/T1 will contribute when it comes to future trends in servo systems?
Important features of servo systems made possible using RZ/T1 include FFT and vibration suppression. We have finished evaluating current and speed control loops, and we will begin evaluating position control next. We are planning reference kits for servo drives using RZ/T1, taking these results into consideration, and will be able to respond to industry demand. Also, in order to enjoy the performance of RZ/T1, we plan to research things like an internal multi-protocol encoder interface, vibration frequency specification and control, and automatic determination of parameters. We expect RZ/T1 to allow further advances in the development of high-performance servo drive control technology.
Thank you very much for your time. Your research with the RZ/T1 shows that even higher performance is desired for servo drive control technology. We look forward to the results of your research.
Highly Integrated Devices Substantially Reduce Design Complexity
Interview with R&D Manager of Germany-based Company K
May I first ask for your introduction? What kind/type of product are you developing and for which market?
As a part of my job as the R&D manager for control engineering at Company K, I am responsible for selecting our strategic microcontrollers. Company K, a manufacturer of FA equipment, is a German manufacturer of drive technology, including electromechanical products like motors, gears, clutches, and brakes, as well as electronic products like frequency inverters, servo drives, PLCs, and motion controllers. Our products are used by all kind of machine builders. Some examples are plastic machinery, textile machinery, woodworking, and renewable energy.
To where do you implement Renesas RZ/T1 into your application and may I ask the reason why you have selected this device?
The RZ/T controllers will be used in in our frequency inverters and servo drives. We mainly chose Renesas products because of their performance (SH), wide product portfolio (H8), and the excellent quality (all devices). We have used Renesas controllers since the H8/3048 and our latest products are equipped with SH2A controllers. Starting from this point RZ/T1 is the logical migration path to higher performance. In addition to that, the RZ/T1 is a highly integrated device that includes dedicated peripherals for real-time Ethernet communication, encoder interfaces, and delta-sigma current sensors interfaces. Due to the fact that this functionality was, in the past, implemented by using external devices like FPGA’s using RZ/T leads to a significant reduction of design complexity. Of course, it also is a chance to reduce the total material costs by more than 25%.
How was your impression after you’ve actually touched RZ/T1?
Although we are still in an early stage of evaluation, I can say that especially the decision to select the Cortex®-R4 core instead of a standard Cortex®-A7 or Cortex®-A9 is highly appreciated. This leads to very good real-time capabilities compared to other ARM based competitors. Interrupt response times are on the same level as they are on an SH system. The combination with the Cortex®-M3 based R-IN Engine allows us to separate the communication and user interface tasks from the motion control part of the servo system of the application. Support for the RZ/T series is another advantage of Renesas development tools. This reduces our efforts when we switch to RZ/T1 based projects.
What would you request for our next gen RZ/T1 and toward Renesas?
Of course the first response of a software developer is that we would like to have more performance. I am sure the next RZ/T1 generations will come up with a higher clock for the Cortex®-R4. From my point of view, it is also important to increase the performance of the R-IN Engine sub-controller because according to all the requirements of IoT and Industry 4.0, the part of the application that is handled by the R-IN Engine will increase. This includes also operating system support, maybe like in the Renesas Synergy software platform. In terms of the integrated real-time Ethernet interface, support for “POWERLINK” would be important.
Thank you sharing with us the view from the perspective of product development. Based on your valuable suggestions for our next gen product, Renesas will continue developing products to meet the needs of product planners and developers.
RZ/T1 Motion Control Solution Kit Supports Fast Development
Although the two people we spoke to in this section are on the front lines of cutting-edge research and development, this doesn't mean that the RZ/T1 is only for people who possess specialized technical knowledge. Renesas offers the RZ/T1 Motion Control Solution Kit, which makes it possible to develop high-speed, high-precision AC servo drives and industrial robot systems in a short time. This kit contains the environment necessary for driving a servo motor. It is possible to start evaluation and development while driving a motor in 30 minutes after opening the kit. The kit also contains board design information and source code for software control, so it helps to vastly shorten development time. Check it out here.