Research And Design Of Controller Of Embedded CIP-Ⅰ Leg Based On UClinux

Intelligent bionic artificial leg(IBAL)has been an interesting research project in the fields of robotics and biomedical engineering. Its excellent characteristic is that it can imitate the movement ways of human healthy leg and its walking speed can change naturally with the change of leg-amputee's walking speed. The research on this project is of practical significance to improving the living situation of leg-amputees and promoting the development of Chinese welfare benefits.The swing of an IBAL is produced by the movement of the piston of the pneumatic cylinder, which is mounted in the knee joint. The motor, which is located at the tail of the pneumatic cylinder, is used to control the opening of a needle valve in the cylinder. Through changing the opening of the valve, the flexion and extension speed of the knee joint can be adjusted, so a suitable walking speed can be obtained. The intelligent artificial legs developed several years ago in some foreign countries have three shortages. The first is that the controllers of these legs, which are used to control the opening of the needle valve of pneumatic cylinder, usually are an open-loop system with a stepping motor. This kind of controllers has lower position precision. The second is that the microprocessors used in these legs mainly are 8 bit or 16 bit single chip, whose running speed cannot satisfy the requirement of advanced control algorithms. Finally, the former system has difficulty in development and expansibility.We developed an innovative intelligent bionic artificial leg, named CIP-I Leg. Aimed at the above three shortages, this paper brought forward a design project of CIP-I Leg's controller based on embedded system to solve the shortcomings. The hardware of the controller includes ARM embedded chip S3C44BOX used as the main CPU, a SST39VF160 chip used to constitute the Flash memory system of the controller, and a HY57V641620 chip used to constitute the SDRAM memory system. In the design of software, uClinux is employed as the OS(Operation System) because its kernel is simple, high performance, revisable and transplantable. In our system, including constructing the tool chain, designing the booting program BootLoader, configuring and transplanting the kernel, developing the device drivers and applications, and so on. On the other hand, a servo DC motor was adopted to replace the stepping motor, and a three close-loop control scheme with position, speed, and current feedbacks was designed for controlling the opening of the needle valve. In addition, an improving ant colony system algorithm was employed to optimize the parameters of the nonlinear PID controller. These improvements of control strategy raised the respond speed and accuracy of the walking speed adjustment.The research in this thesis is about an improvement design on the control system of the first archetypal machine of CIP-I Leg, which has high practical value to accelerate its entering into the business market.