Residual Vibration Reduction of High-Speed Pick-and-Place Parallel Robot Using Input Shaping

Because of their elastic links and joints,high-speed parallel robots for pick-and-place operations inevitably suffer from residual vibrations that significantly degrade their positioning accuracy.An effective approach based on the input shaping technique is presented in this paper for suppressing the residual vibration in these parallel robots.After addressing the design principle of an input shaper for a parallel robot with flexible actuated joints,a robust optimal input shaper is developed by considering the configuration-dependent flexible modes and minimizing the maximum percentage of residual vibration at the end-effector.The input shaper allows a good overall performance to be achieved throughout the entire workspace.Experimental results on a 4-DOF SCARA-type parallel robot show that the residual vibration of the end-effector is dramatically reduced and the dynamic positioning accuracy of the robot significantly improved.

Comparative analysis on the performance of different types of input-and command-shaping controllers in minimizing payload residual vibration of an overhead crane with an inclined supporting track

Reducing the effects of external disturbance on overhead crane systems is crucial,as they can impair the controller performance and cause excessive vibrations or oscillations of the payloads.One such external disturbance is the inclination of the supporting track of the crane trolley,which causes the system dynamics model to change.An open-loop control strategy is widely utilized to control the payload sway motion and generally does not require any alterations in the physical structure of a system or the installation of sensors and/or actuators.Input and command shaping are two common open-loop control techniques applied to control overhead cranes.In this paper,the effect of moving an overhead crane system along an inclined supporting track is investigated.In addition,the ability of different types of input-and command-shaping control schemes to suppress the residual vibrations due to trolley track inclination is demonstrated.Two types of input-shaping controllers,which are double-step,zero vibration,and one command waveform(WF)shaper based on a trigonometric function,are used and tested.A linear equation of motion of the overhead crane resting on an inclined surface is developed to simulate the overhead crane and payload motion.The effectiveness of the different types of open-loop controllers to suppress residual vibrations is verified by both simulation and experimental results.In addition,a new WF command shaper is proposed and designed to overcome track inclination while eliminating payload residual vibration.A comprehensive comparative analysis,both numerically and experimentally,is performed on the new proposed shaper to measure its effectiveness in handling inclination when compared to other types of open-loop controllers.The new shaper outperforms other controllers in eliminating payload residual vibration for a wider range of inclination angles.

Data Driven Vibration Control:A Review

With the ongoing advancements in sensor networks and data acquisition technologies across various systems like manufacturing,aviation,and healthcare,the data driven vibration control(DDVC)has attracted broad interests from both the industrial and academic communities.Input shaping(IS),as a simple and effective feedforward method,is greatly demanded in DDVC methods.It convolves the desired input command with impulse sequence without requiring parametric dynamics and the closed-loop system structure,thereby suppressing the residual vibration separately.Based on a thorough investigation into the state-of-the-art DDVC methods,this survey has made the following efforts:1)Introducing the IS theory and typical input shapers;2)Categorizing recent progress of DDVC methods;3)Summarizing commonly adopted metrics for DDVC;and 4)Discussing the engineering applications and future trends of DDVC.By doing so,this study provides a systematic and comprehensive overview of existing DDVC methods from designing to optimizing perspectives,aiming at promoting future research regarding this emerging and vital issue.

NEW DESIGN OF ROBUST OPTIMAL ARBITRARY TIME-DELAY FILTER

Zero placement method in the frequency domain is utilized to design robust multi-hump EI optimal arbitrary time-delay filter （OATF） by placing two or more filter zeros near the system poles. A total insensitive OATF can be also achieved if the problem of insensitivity to damping errors is considered. This design strategy is easier to derive and implement. Applications in the anti-swing control of overhead cranes verify the fine performance of this strategy. A better suppression of the load vibrations is obtained using the proposed new OATF, which is more robust to the variation of the cable length.

调控管道声波以主动抑制高精度喷墨打印中的次级液滴

按需喷墨打印技术主要依赖于通道内的声波来实现液滴的喷射,其在气体环境中的各前沿领域发挥了不可取代的作用.喷墨打印液滴直径通常在20–100微米范围内,难以进一步减小.对于管道声波触发的受约束界面的振动而开发的新兴的液中高精度打印技术,其可以产生小于喷嘴直径数十倍的液滴,并可以灵活地调整液滴尺寸.然而,当激励很强的时候,受约束界面的残余振动会产生次级液滴,进而影响打印的均一性.在此,本文提出了通过调控管道声波进而调控界面行为的策略,在实现显著主振动的同时有效抑制残余振动.基于实验现象构建了数学模型以描述界面行为是如何调控的,回波时间对界面振动的影响,残余振动影响后续主振动和主液滴的机制都得到了较好的解释.本文的工作为通过调控管道内的声波来调控液滴尺寸和改善打印精度提供了理论指导,并证实了其实际应用的潜力.

Nonlinear identification of electro-magnetic force model

Conventional attractive magnetic force models (proportional to the coil current squared and inversely proportional to the gap squared) cannot simulate the nonlinear responses of magnetic bearings in the presence of electromagnetic losses,flux leakage or saturation of iron.In this paper,based on results from an experimental set-up designed to study magnetic force,a novel parametric model is presented in the form of a nonlinear polynomial with unknown coefficients.The parameters of the proposed model are identified using the weighted residual method.Validations of the model identified were performed by comparing the results in time and frequency domains.The results show a good correlation between experiments and numerical simulations.