Robust Control of Welding Robot for Tracking a Rectangular Welding Line

Abstract

This paper highlights a welding robot (WR) for its end effector to track a rectangular welding line (RWL). The WR includes five actuators which use a DC motor as a power source. Two controllers are proposed to control the WR's end effector: a main controller and a servo controller. Firstly, based on WR's kinematic equations and its feedback errors using backstepping method the main controller is proposed to design the reference-inputs for the WR's actuators in order that the WR's end effector tracks the RWL. Secondly, based on the dynamic equation of WR's actuator, the servo controller is designed using an active disturbance rejection control method. Finally, a control system incorporated with the main controller and the servo controllers make the WR's end effector robustly track a RWL in the presence of the modeling uncertainty and disturbances during the welding process. In experiment, the main controller which has a function as a master of the control system links to the five servo controllers which have a function as a slave via I2C communication. The effectiveness of the proposed control system is proven through the simulation and experimental results.

Keywords

• A welding robot
• backstepping method
• active disturbance rejection control method
• rectangular welding line (RWL)
• extended state observer (ESO) Nomenclature: & & y
• z : Linear velocities of vertical and horizontal sliders
• respectively [ m / s] : Angular velocities of vertical and y
• z 1
• 1 horizontal slider's motors
• respectively [ rad / s] : Rotational angle of torch's direction with respect to y axis and its angular velocities [ rad ]
• [ rad / s] 2
• 2 w [ rad / s] vr : Rotational angle and angular velocity of : Angular velocity of the weaving motors : Reference welding velocity [0.007 m / s] : Angle between projection of v r on the x axis tracking motor [ rad ]
• [ rad / s] plan ( y
• z ) and the z axis [ rad ] : Angle between projection of v r on the plan ( x
• z ) and the z axis [ rad ] : General rotational angle of DC motor's rotor [ rad ] f () : Modeling uncertainty and unknown disturbance of the actuator.