APPLICATION OF HIERARCHICAL MODEL METHOD ON

OPEN CNC SYSTEM’S BEHAVIOR RECONSTRUCTION

Yongxian Liu, Chenguang Guo, Jinfu Zhao, Hualong Xie

Institute of Advanced Manufacturing and Automation, Northeastern University, Shenyang, Liaoning, China

Weitang Sun

Shenyang Institute of Computer Science, Chinese Academy of Sciences, Shenyang, Liaoning, China

Keywords: Finite state machine, Hierarchical model, State table, Behavior reconstruction.

Abstract: There are many shortcomings in the open CNC system control program developed by the traditional

programming mode, such as maintenance difficulties and poor portability. The application and development

of FSM in CNC system are researched in this paper, and the basic principles of FSM and reconstruction

mechanism of FSM are introduced. The reconstruction process based on FSM by the application of

hierarchical modeling method and status table are also constructed. At last, the adaptive control function of

automatic adjusting feeding speed in three axis CNC milling machine is extended to realize the function

definition of the software unit in control system and control logic separation.

1 INTRODUCTION

NC system is an abbreviated form of numerical

control system. It is a complex multi-tasking

controller with different levels of real-time

requirements. In the system, each object's function,

behavior, starting process and their mutual

relationships between the operating system modeling

must be a clear description. This is directly related to

the system's performance and operating reliability.

Kruth et al. (2001) use FSM to model the planning

and monitoring knowledge in Machine tool control.

Li et al. (2005) apply a hierarchical finite state

machine to the system behaviors' model o improve

the reconfigurability in an open architecture control

system. Ma et al. (2007) propose a dynamical

behavioral modeling and describe it in hierarchy

finite state machine model. Aiming at the

characteristics of modularity and reconfigurable in

open architecture computer numerical control (CNC)

system, Wang et al. (2007) adopted finite state

machine to create the dynamically modeling. Lid et

al. (2008) use hierarchic finite state machine to

describe dynamical behaviors of the controller.

Using FSM method, the machine control flow can be

separated with the mechanical parts, and it can be

changed separately. This approach greatly increases

the openness of the CNC system by limiting the

control program which depends on the particular

machine behavior and operating in a local part.

Based on the working principle and the hierarchical

modeling method of finite state machine, we create

the model of complex system to explore the

application of finite state machine in numerical

control system software development process.

2 THEORETICAL

BACKGROUND

2.1 Finite State Machine

Finite state machine consists of the following

elements:

1) State: The basic component of behavioral

model. It reflects the stage and activity of an object

in the system.

2) Transfer: The process from one state to

another state of the objects.

3) Event: The events and conditions that caused

the state transformation of object.

4) Action: The action of object when the state

changes.

172

Liu Y., Guo C., Zhao J., Xie H. and Sun W. (2010).

APPLICATION OF HIERARCHICAL MODEL METHOD ON OPEN CNC SYSTEM’S BEHAVIOR RECONSTRUCTION.

In Proceedings of the 7th International Conference on Informatics in Control, Automation and Robotics, pages 172-175

 SciTePress

indicates the action triggered in the transfer process

of object.

Figure5: Change of FSM state.

As shown above, it is very convenient and

efficient to change status table with the method

provided by FSM base class library. In addition,

module developers still need to complete the

programming of

AdjustAction and

DoneAction.The following is part codes of

AdjustAction (), it can realize the function of

speed adjustment.

Currently popular adaptive speed control

algorithm can be added in the above codes to satisfy

all kinds of needs of users. According to adding

speed regulating adaptive control functions in three

axis CNC milling machine, the open CNC system

can integrate other external sensor signals to

implement users’ unique control strategy.

5 CONCLUSIONS

As the dynamic behavior model of the system, FSM

has the ability of behavior reconstruction. This

method greatly increases the openness of the system.

The model of behavior which is based on finite state

machine stipulates the system behavior and control

flow, cuts down the development cycle of the CNC

system and enhances the reliability of the system. At

the same time, FSM model can realize the function

definition and control logic separation of software

unit. It can improve flexibility of system

reconstruction. Finally, the system’s reconstruction

based on finite state machine represents the

reconstruction of state table. This can simplify the

reconstruction process of the numerical control

system absolutely.

ACKNOWLEDGEMENTS

This work was supported by Major national science

and technology special projects during the 10th five-

year plan (No. 2006BAF01A19), Key Scientific and

Technological Project of Liaoning Province (No.

2006219008), Key Scientific and Technological

Project of Shenyang City (No. 1071114-2-00),

Postdoctoral Science Foundation under Grant

20080441093 and Key Laboratory Foundation of

Liaoning Province under Grant 2008S088.

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