Professor Takita of the National Defense Academy of Japan has had a long involvement in the research and development of self standing robots that can be controlled remotely by an operator. The Octal Wheel, an eight-wheeled robot able to climb over uneven terrain, can be seen as the culmination of this research. Since around 2000, professor Takita has been using Renesas microcomputers for this and many other robot designs. He is particularly impressed by the availability of our development systems.

Professor Takita has a long history in the field of robotics research. About twenty years ago he built a walking robot with four legs arranged diagonally. Since then he has developed a number of different types, including a quad ruped robot, an iron-bar robot, and an inchworm robot. More recently, at venues such as the IROS 2004 international conference held in Sendai, he has presented papers describing his eight-wheeled Octal Wheel robot, a design that can travel over uneven terrain. He also entered the second Japan Micom Car Rally (run by the Japan Micom Car Organizing Committee, sponsored by Renesas), where he enjoyed victory

The direction of his robotics research is clear. "Because getting an autonomous robot to do what you want is difficult, my research focuses on independent robots that operate under the control of a person. One example is a rescue robot that can climb over steps and go where people cannot," explained Professor Takita.

The inchworm robot has the required mobility. It consists of five 300mm ring sections and can climb stairs and similar obstacles. The Octal Wheel machine is a mobile robot of an entirely different design. It uses a 4WD+4DS configuration with four front wheels and four rear wheels (see photograph). "Mobile robots that move using legs cannot walk forward unless they can determine the conditions that exist where they are about to place their feet. This means that these robots need sophisticated sensors if they are to satisfy the requirement of being able to go anywhere. In contrast, robots that move on wheels are more practical because they can move simply by rotating their wheels, which are already in contact with the ground. We chose to give our robot eight wheels to ensure that it would be able to cope with the task of going up and down stairs," said Professor Takita.

In the design of the Octal Wheel robot, Renesas H8S/2258 microcomputers were chosen for two types of applications: the motor controllers and the host CPU (see figure). "When using rotary encoders for motor control, the software becomes complex unless there is a separate phase-count interface for each motor. The two channels that the H8S/2258 microcomputer provides make control easy," Professor Takita said.

The Octal Wheel consists of the robot unit and a separate controller connected via a radio link. The operator remotely controls the robot while viewing the image from a CCD camera mounted on the robot unit. A Renesas H8S/2258 device is also used in the controller.

The model car for the Micom Rally is self-guided by an onboard camera that detects a white line on the race course. It, too, uses an H8S/2258 microcomputer. In the model car the chip performs various functions, including processing the input from the camera to extract the line image.

Professor Takita started using Renesas microcomputers about six years ago. Subsequently, he has made extensive use of these devices for various purposes in a number of different robots. Recently, he has used an H8/3048 chip for motor control and a SH7145(SH-2) for host controller in a student competition for GPS-controlled robot cars, and won the race. He also makes active use of them in his day-to-day teaching.

"In the past, we used assembly-language programming. Now, however, software development is much easier because the SuperH and H8 family supports programming in C. Another feature of the microcomputers that is particularly convenient is the ability to update the program in internal flash memory as required," he explained. Professor Takita also commented that the overall development environment for the chips is a key feature he rates highly. In particular, he mentioned that Renesas offers low-cost evaluation boards and provides at no cost the evaluation version of the High-performance Embedded Workshop (HEW) integrated development environment. HEW has a familiar look and feel and includes a complete software toolchain, project management tools, and a Project Wizard, as well as the Flash Development Toolkit (FDT) for programming the on-chip flash memory.