Intelligent Controller Based On Ant System Algorithm And Fuzzy Inference And Its Application To Bionic Artificial Legs

Intelligent artificial leg has been an interesting research project in the fields of robotics and biomedical engineering. It incorporates many important subjects, such as intelligent control, microelectronics, computer technology, mechanical design & manufacture, biomedical engineering, etc. The most excellent characteristic of intelligent artificial leg is that it can imitate the movement way of human healthy leg and its walking speed can be naturally adjusted with the change of amputee's walking speed. The significance of this research is that it can help amputees to return to the mainstream society and lighten the burden of the society and their families.The swing of an intelligent artificial leg is produced by the movement of the piston of the pneumatics cylinder, which is mounted in the leg. The motor, which is located at the tail of the pneumatics cylinder, is used to control the opening of a needle valve in the cylinder. Through changing the opening of the valve, the bending and extension speed of the knee joint of the leg can be adjusted, so a suitable walking speed can be obtained. The intelligent artificial legs produced several years ago in some foreign countries, such as Japan and United Kingdom, have two shortages. One is that the controllers of these legs, which are used to control the opening of the needle valve of pneumatics cylinder, usually are an open-loop system with a stepping motor. This kind of controllers has lower position precision and no intelligent behavior. The other is that the microprocessors used in these legs mainly are C51 single chip, whose running speed cannot satisfy the need of advanced control algorithms.In this research, aimed at the above two shortages, the following improvements were made. Firstly, a servo DC motor was adopted to replace the stepping motor, which can make the controller realize accurate position control in great scope. Secondly, a close-loop control scheme was proposed for the movement of the needle valve. In the design of the controller, an improving ant system algorithm was adopted, which was used to optimize the parameters of the controller. At the same time, fuzzy logic control was also used to adjust the parameters of controller in realtime. The improvement of control strategy raised the respond speed and accuracy of gait adjustment of the intelligent artificial leg. Lastly, in the design of the controller hardware circuits, MSP430F149 chip produced by Texas Instruments (TI) was adopted as the CPU of the intelligent controller. MSP430F149 is a kind of IC with excellent performance, which has the characteristics of ultra-low-power and highly integrated degree. Its running speed is faster than C51 single chip and has powerful instruction system. MSP430F149 chip can complete easily the on-line operation of many advanced control algorithms. Its special hardware structure brings great convenience to the hardware and software design of the intelligent controller.The author has designed and made the hardware circuits of the intelligent controller, and written control software. From the experiment result, it was concluded that the controller of intelligent artificial leg designed in this research has better intelligent behavior, robustness, response speed, and accuracy.