To promote operational intelligence, improve surface quality, and reduce manpower dependence, a novel high-bandwidth end-effector with active force control for robotic polishing was proposed. Using this end-effector as a mini robot, a macro-mini robot for polishing processing was constructed, in which the macro robot provides posture control during polishing operations, whereas the mini-robot provides constant force control. By minimizing the inertia along the spindle in this configuration, the end-effector obtains a force control bandwidth of 200 Hz. Through a series of comparative experiments with different contact forces and feed rates, the proposed design was proven to have a smaller overshoot, a faster response, and a shorter settling time than the conventional method based on macro robot (KUKA iiwa) controlled force. The roughness of the workpiece reached 0.4 μm after polishing with the macro-mini robot, indicating the efficiency of this end-effector in high-precision material removal and surface polishing operations.

Industrial robots are increasingly being considered for application in performing polishing operations. Most research has been performed on workpieces with a priori (CAD) model, and used impedance control or hybrid force-position control to achieve constant force operation. For workpieces without priori models, it is still difficult to maintain a constant normal contact force during the polishing process. To address this challenge, this paper proposes a cooperative force-position control method consisting of three parts: constructing a model between contact forces and robotic poses during polishing operations and obtaining a real-time pose deviation of the current tool-workpiece contact state and the desired (normal) contact state; based on the deviation, a method of real-time adjustment of 2D predefined polishing paths to 3D actual polishing paths is proposed; finally, constant normal contact force control is achieved by a direct force control algorithm based on the results obtained from the above method. The proposed method is based on a macro-mini robotic system with an active force control polishing device, and its effectiveness was tested by various unknown-model workpiece polishing scenarios. The results demonstrate that the proposed method can achieve stable normal force tracking and high-quality surfaces during unknown-model workpiece polishing.

As a result of such advantages as flexibility, high freedom, large working space, and low price, the use of industrial robots instead of a traditional numerically computer controlled polishing machine and artificial polishing has become a popular research topic. Over the years, researchers have been studying robotic polishing to improve the shape accuracy, roughness, and consistency of the workpieces surface. In this paper, the content of robotic polishing research is reviewed, covering the type of robotic polishing systems, material removal prediction, and high-quality workpiece surface obtained. In addition, some potential difficulties and challenges are discussed and analyzed. This paper could be used as a reference for researchers who choose a relevant research target and a method for developing an applicable robotic polishing system.

In order to improve the detection accuracy of objects at different scales, the most recent studies applied multilayer architecture. However, the extracted low-level feature in the shallow layers may not work perfectly on the detection performance due to its less semantic information, especially for small objects. In this paper, we propose a refined feature-fusion structure to be integrated with single shot detector (SSD). To obtain the rich representation ability for feature mapping, in the fusion block, the deconvolution operation is basically applied to fuse high-level semantic features and low-level semantic features. It is noteworthy that in the proposed framework, the feature pyramid network is modified to better describe the features by the skip connection. An adaptive weighted connection is designed at the feature-fusion block, which further enhances the performance of the detection. On PASCAL VOC2007 test set, the experimental results show that the mAP of the proposed network is higher than SSD and deconvolutional single shot detector (DSSD) by 2.03% and 0.63%, respectively. Meanwhile, the speed of our method is as 2.2 times fast as the DSSD. Furthermore, the mAP of our refined feature-fusion structure SSD is 6.2% higher than SSD on the small object test set of PASCAL VOC2007, which verifies the effectiveness of the proposed model.

In order to realize the compliant active-force control of polishing robots, a novel end effector was designed. According to the characteristics and technical requirements of polishing process, Axiomatic Design was employed to define the function, behavior and structure of the robot end effector, and a novel polishing mechanism was proposed. The response characteristics and frequency domain characteristics of the actuator's electromechanical system were analyzed in detail. The polishing actuator realized the decoupling of the tool force control and the position control. Experiments showed that the designed robotic polishing end effector has an excellent compliance performance.