ORIENTAL MOTOR CO., LTD.

Switching to a SuperH Microcomputer Achieves 4000-rpm Operation Using C Programming

"ORIENTAL MOTOR 'S αSTEP series of stepping motors uses a new concept of sensor-based control and we have put a lot of development effort into this product line. Whereas the fastest speed we had been able to achieve in the past using 16-bit microcomputers was about 2000 rpm, our switch to the 32-bit SuperH family immediately allowed us to increase the motor speed up to 4000 rpm. This high level of performance makes the αSTEP series of motors strong sellers," commented Mr. Itabashi. "Not only that, we were able to put the excess processing capacity in the microcomputer to work in the simultaneous execution of a vibration suppression function using data from a position sensor. So the SuperH chip both doubled performance and added an important selling feature," he added.

Subsequent products have been implemented using SuperH family models with built-in flash memory. "The on-chip flash eliminates the need to replace one-time ROM versions of the SuperH family. This has enabled a big improvement in our development efficiency. Also, it allows us to provide the latest version of the development software on our motors and hardware groups," explained Mr. Itabashi. Whereas a memory capacity of 64Kbytes was adequate for the earliest αSTEP stepping motor models, the number of program steps has grown every year, as the code has become more added to increace functions. The latest αSTEP models now require 256Kbytes of flash.

In terms of development efficiency, ORIENTAL MOTOR rates the SuperH family highly because the C programming language can be used for development. "Once I saw the code produced by the C compiler for the SuperH family, I was confident that these Renesas 32-bit RISC microcomputers could be used to control a motor and deliver strong performance in the real world. Even when programmed using assembly language, the 16-bit microcomputers we previously used could only handle speeds up to around 2000 rpm. Devices in the SuperH family, on the other hand, can control motors running at 4000 rpm using a program written in C," Mr. Itabashi said.

Since 2003, ORIENTAL MOTOR has also been selling actuators that incorporate the αSTEP series or other motors. The actuator product line includes electrically driven sliders and cylinders, new designs of compact actuators, and linear motion systems such as linear heads. "Most of our customers use our motors in linear motion systems. We facilitate that use by incorporating the parts that work directly with the motors into ready-to-use assemblies," Mr. Itabashi explained. One of the products in this range of actuators is the "EZ Limo" series of electrically driven sliders (see Photograph 2), which use Renesas SuperH microcomputers.

Mr. Itabashi has an expectation that the SH-2A core will play a role in the development of future ORIENTAL MOTOR products. "Obtaining more microcomputer processing performance is essential to improving the precision with which we can bring a high-speed rotating object to a rapid halt at the correct position. We are looking forward to using chips with the SH-2A core and internal FPUs (floating point units), for example. Those devices will help us implement designs that deliver the greater speed and precision that our customers soon will be seeking," said Mr. Itabashi.