Embedded Flat Knitting Machine Control System Design

Flat knitting machine is the main equipment for the production of knitted sweater. It can knit yarn which made of cotton, feather, hemp, silk, pashm ,chemic fibre. The conventional handcrafted machine is inefficient. The quality of the production is not well, but the cost is high. Computerized flat knitting machine is a kind of versatile knitting machine. With application of the new technologies include computer control, electronics, mechanism, knitting technics and so on, computerized flat knitting machine realized the automation in weaving production. It's certain that handcrafted machine will be replaced by computerized flat knitting machine.The characteristics and development of embedded system is introduced in the beginning of this paper. Then, on the base of the analysis of flat knitting technics and the technology of embedded system, a new kind of computerized flat knitting machine is designed. With the theory of hierarchical control, this control system is divided into three level, include supervisory level, main control level, the bottom control level. The CAN bus is used to communication to each other..The supervisory level which is consist of a 32 bits ARM processor, LCD, keyboard, USB interface, is main used for human-machine interface. Pattern files inputted by USB interface, is transferred to the main control level through CAN bus. Compared with floppy interface, this scheme is more efficient and reliable.The main control level also use ARM as CPU. A Flash which has big capacity of 8MB is used to make sure successfully input of big pattern files. This level is responsible for the correspondency and control of the whole system.The bottom control level control the actuators which lie on the head of flat knitting machine. It make the solenoids, electronic selectors, stepper motor act follow the request of knitting technics. TI's DSP is used as CPU, and Altera's CPLD is used for system extending which include I/O extending, address coding, generating impulse for stepper motor. This is useful to improve the process speed.Using the hierarchical control mode, the control of the head of machine is separated from the main control level. This is fitter for the mechanical construction of flat knitting machine, and making the system's construction more clear and reliable. Compared with the scheme which control all the actuator with only one control level, this mode is more reliable and efficient.