Abstract
Installing force-controlled end-effectors on the end of industrial robots has become the mainstream method for robot force control. Additionally, during the polishing process, contact force stability has an important impact on polishing quality. However, due to the difference between the robot structure and the force-controlled end-effector, in the polishing operation, direct force control will have impact during the transition from noncontact to contact between the tool and the workpiece. Although impedance control can solve this problem, industrial robots still produce vibrations with high inertia and low stiffness. Therefore, this research proposes an impedance matching control strategy based on traditional direct force control and impedance control methods to improve this problem. This method’s primary purpose is to avoid force vibration in the contact phase and maintain force–tracking performance during the dynamic tracking phase. Simulation and experimental results show that this method can smoothly track the contact force and reduce vibration compared with traditional force control and impedance control.
Highlights
In automobile, aerospace, medical equipment, and other industries, most metal workpieces are formed through welding, casting and other necessary processing procedures
The polishing process produces a large amount of dust, corrosive chip fluid and noise, which can lead to safety accidents resulting in operators’ injury [1,2,3]
Whether impedance control or direct force control is adopted, the vibration of contact force decreases obviously with impedance matching in the whole polishing process
Summary
Aerospace, medical equipment, and other industries, most metal workpieces are formed through welding, casting and other necessary processing procedures. An industrial robot called a macro manipulator and the end-effector called a mini manipulator constitute a macro-mini manipulator system This method is often used in medical surgery [14], assembly [15], polishing [2] and other tasks requiring precise force control. Chen [19] proposed a novel 3-DoFs (Degree-of-Freedom) linear magnetic actuator, which increases the damping and static stiffness of flexible structures during machining These methods could effectively reduce the vibration in a series macro-mini manipulator system, but the structure is complex and the cost is high. Li [33] proposed a zero-coupling impedance theory based on the macro-mini manipulator, which could theoretically improve the bandwidth of force control It lacked a damped and rigid end-effector to further illustrate the feasibility.
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