Research on Constant Force Polishing Control of Aero-engine Blade Based on Expanded State Observer

This paper presents a parallel control method based on the expanded state observer (ESO) for aero-engine blade robot polishing. Aiming to reduce the fluctuation of polishing force caused by environmental noise and modeling errors. First, calibrate six-dimensional force sensor according to the maximum acceleration of the end effector during the polishing process. Then, build the gravity compensation and zero drift compensation model. Besides, use this model to compensate measurement error of the six-dimensional force sensor. Finally, calculate the error between the expected polishing force and the actual feedback value and its derivative value. Use calculation results to design the control boundary layer. The polishing force controller is divided into two parallel control loops to design. When the switching value is in the control boundary layer. A nonlinear active disturbance rejection control (ADRC) loop is used. When the switching value is outside the control boundary layer. An ESO-based sliding mode control (SMC) loop is used. Simulation and experimental results show that the proposed parallel control method based on ESO has a fast response and high robustness compared with FuzzyPID, PID, and ADRC. It can effectively suppress the force fluctuation in the polishing process and significantly improve the surface processing quality of the aero-engine blade.

Study on Flexible Polishing Force and Polishing Temperature of Flap Disc

Polishing determines the final surface quality of the aero engine, which have great influence on its working performance and working life. By analyzing the structure and working principle of the flexible self-adaptive polishing platform of the blisk, the abrasive cutting model of the flap disc is established. The theoretical calculation of the effect of elastic deformation during the polishing process on the contact length of flap disc and blisk. The model of polishing force, polishing heat and temperature field during the polishing process of the flap disc are established and analyzed. Single factor method is used to analyze the influence of process parameters on polishing force, polishing temperature, roughness and specific polishing energy. Finally, the polishing test shows that the optimized process parameters improve the polished surface quality and meet the requirements of the blade polishing process.

Performance Evaluation of Robot Polishing in Macro-Micro System Based Polishing Robot

Polishing is an important process performed in the finishing and repair processes of mechanical parts and is still a manual work of skilled workers. However, in addition to the time and cost required for manual polishing, there are also problems such as a decrease in the number of workers and health hazards due to dust generated during polishing. From these problems, the demand for automatic polishing is increasing at manufacturing sites. To automate polishing process, a macro-micro system based polishing robot which consists of a functional end-effector and industrial robot has been proposed. Regarding end effectors, mechanical design aiming for high rigidity and motion control methods for keeping the contact force constant is being researched. Meanwhile, the tool rotation speed of the spindle is independently controlled typically. Therefore, in this research, a functional polishing module capable of polishing force control and tool rotation control according to the tool feed rate is developed as the end effector. For the polishing automation, the macro-micro system based polishing robot is constructed attaching the polishing module to the industrial robot. From the viewpoint of Preston’s law, the effectiveness of the robot polishing is investigated through polishing experiments and measuring the shape of the polished surface.

Development of robotic polishing/fettling system on ceramic pots

Current robot polishing techniques are available for objects with computer-aided design geometric models but not for objects without geometric models such as ceramic or clay pots. In this study, we developed a robotic polishing/fettling system to polish the molding defects of ceramic objects. The polishing force on the object surfaces is required to be constant to obtain better results. Thus, the proposed robotic polishing system was designed with a stepper motor, ball screw, and force sensor. The proposed system acquired a rough robot polishing/fettling trajectory and adopted a fuzzy proportional–integral–derivative controller to regulate the trajectory to maintain the desired contact force response from a ceramic object. We developed the temporary desired value technique to make the polishing force response close to the desired one. We validated the system on a six-degrees-of-freedom Staubli TX 40L robotic arm. Experiments were performed to test the effectiveness of the system. The robot trajectory responses showed that the proposed system performed well in tracking the desired force in the polishing/fettling process. We used a 3D microscope to verify that the molding defect of the ceramic pot was significantly removed to evaluate the polishing/fettling quality.

Design and control of the belt-polishing tool system for the blisk finishing process

According to the structural characteristics of the blisk, a new adaptive belt tool system for blisk finishing is developed. The pneumatic servo system, which is composed of the cylinder, the servo valve, and the force sensor, is used to control the polishing force. Due to the strong nonlinearity of the pneumatic system, a two-dimensional fuzzy proportion, integral, derivative (PID) controller is developed for the pneumatic force control. The proposed controller adjusts the proportional, integral, and differential parameters of the traditional PID controller in real time through the error and error rate so as to optimize the control performance of the pneumatic system. Compared with the PID control, the steady-state error of the fuzzy PID control is reduced by 0.03 s and the overshoot is reduced by 4 %, which reveals the superiority of the fuzzy PID control algorithm for the nonlinear system. Finally, the experiments of polishing the blisk sample and the real blisk are carried out by the proposed belt tool system. The results show that the polishing process is very stable and the roughness after polishing is less than 0.4 µm, which proves the effectiveness of the proposed new belt tool system and the fuzzy PID controller.

Investigation on Polishing of Zirconia Ceramics Using Magnetic Compound Fluid: Relationship Between Material Removal and Surface Roughness

Zirconia ceramics have excellent applicability in the aerospace, defense, new energy, automotive, electronics, and biomedical fields. However, few investigations have been conducted on the high-precision polishing of zirconia ceramics. In this work, a polishing method using a magnetic compound fluid slurry is proposed. First, the principle and the constructed experimental setup were presented. Then, the experiments were performed that characterized the surface profile after polishing, the effect of the working gap, and the effect of the concentration of carbonyl iron particles (CIPs) on the material removal and surface quality. The results showed that the material removal ability correlated positively with the surface roughness; the smallest working gap (0.5 mm) induced greater material removal ability and better surface roughness; higher CIP concentration enabled a higher polishing force to obtain higher material removal and better surface quality. The polishing results show that surface roughness Rz of 55 nm was obtained at the surfaces of zirconia ceramics, confirming that the proposed method has the potential for polishing of zirconia ceramics.

Preliminary study: Polishing force measurement by viscosity - the return of ketchup polishing

Due to the advantages over conventional polishing strategies, polishing with non-Newtonian fluids are state of the art in precision shape correction of precision optical glass surfaces. The viscosity of such fluids is not constant since it changes as a function of shear rate and time. An example is during the shape correction by polishing with pitch or ice, where pitch flows slowly under its own weight and acts like a solid body during short periods of stress as its viscosity increases. The effect can be measured in the polishing gap with a viscometer. If there is a change in force or a process variation of the polishing pressure in the polishing gap, the viscosity also changes. Conversely, the viscosity value could be used to determine the process variation of the polishing force, at least quantitatively. It is to be expected that the distance of the sensor to the polishing gap (effective zone of the polishing force) and the associated change in the viscosity value has a decisive influence on the accuracy of the measurement resolution. First polishing results will be presented and a bowl feed polishing like approach will be presented

Effects of Anisotropy on Single Crystal Silicon in Polishing Non-Continuous Surface

A molecular dynamics model of the diamond abrasive polishing the single crystal silicon is established. Crystal surfaces of the single crystal silicon in the Y-direction are (010), (011), and (111) surfaces, respectively. The effects of crystallographic orientations on polishing the non-continuous single crystal silicon surfaces are discussed from the aspects of surface morphology, displacement, polishing force, and phase transformation. The simulation results show that the Si(010) surface accumulates chips more easily than Si(011) and Si(111) surfaces. Si(010) and Si(011) workpieces are deformed in the entire pore walls on the entry areas of pores, while the Si(111) workpiece is a local large deformation on entry areas of the pores. Comparing the recovery value of the displacement in different workpieces, it can be seen that the elastic deformation of the A side in the Si(011) workpiece is larger than that of the A side in other workpieces. Pores cause the tangential force and normal force to fluctuate. The fluctuation range of the tangential force is small, and the fluctuation range of the normal force is large. Crystallographic orientations mainly affect the position where the tangential force reaches the maximum and minimum values and the magnitude of the decrease in the tangential force near the pores. The position of the normal force reaching the maximum and minimum values near the pores is basically the same, and different crystallographic orientations have no obvious effect on the drop of the normal force, except for a slight fluctuation in the value. The high-pressure phase transformation is the main way to change the crystal structure. The Si(111) surface is the cleavage surface of single crystal silicon, and the total number of main phase transformation atoms on the Si(111) surface is the largest among the three types of workpieces. In addition, the phase transformation in Si(010) and Si(011) workpieces extends to the bottom of pores, and the Si(111) workpiece does not extend to the bottom of pores.