Abstract
When tracking the trajectory of the mechanical arm in a joint space, the system is affected by friction non-linearity, unknown dynamic parameters and external disturbances that makes it difficult to improve the control accuracy of the mechanical arm. To solve the above problems, this paper introduces LuGre friction model and designs a new joint space trajectory tracking controller based on the adaptive fuzzy neural network. The controller is capable to make the adaptive adjustment of the center and width of the basis function, can approach the nonlinear link having the LuGre friction on line, and uses the sliding mode control term to reduce the approximation error. The introduction of LuGre model into the mechanical arm system can more truly simulate the friction link of the system, which is of great significance to the high precision control of the mechanical arm. The Lyapunov method is used to prove the stability of the closed-loop system. The simulation results show that the designed adaptive fuzzy neural network can effectively compensate the non-linear links including friction without precise system parameters, and the controller has strong robustness to load changes, thus realizing high-precision trajectory tracking of the mechanical arm in joint space.
Highlights
Mechanical arm has been widely used in industrial manufacturing, agriculture, medical and other fields
The parameters of the joint space trajectory tracking controller based on the fuzzy neural network are selected as follows: parameter k is related to the steady state accuracy of the system, a large overshoot may occur when the k value is too large, this number shall take a moderate value; parameter K significantly affects the convergence speed of the sliding mode surface and the steady-state accuracy of the system, this parameter shall be a large value; parameter K can restrain the approximation error of the fuzzy neural network and system disturbance, this parameter shall be a moderate value
The LuGre friction model was introduced into the mechanical arm system
Summary
Mechanical arm has been widely used in industrial manufacturing, agriculture, medical and other fields. The LuGre friction model [8,9,10,11,12,13] is a perfect dynamic friction model proposed by Cannudas et al, which can more accurately describe the complex dynamic and static characteristics in the friction process, such as sliding displacement, friction hysteresis, variable static friction, creep and Stribeck effect, etc Researchers have done a lot of work [14,15,16,17,18,19] to compensate the nonlinearity and parameter uncertainty of mechanical arm dynamics using appropriate methods, so as to realize the accurate trajectory tracking of the mechanical arm. Simulation experiments indicate the efficiency of the suggested controlling method
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