Backlash Problems Research Articles

Governing of a Francis Turbine Model Subjected to Load Variations

In this work, the problem of mechanical backlash in the governor system for the Francis test rig at the Waterpower Laboratory, NTNU Trondheim, is investigated. Through numerical simulations on a digital model of the test rig, done in the software SIMSEN, the maximum allowable backlash which still enables stable governing was detected. This was done by further developing the model used in the work by A. Ingranata [1], to perform load variation tests presented by Statnett [2]. From these frequency control tests it was concluded that the maximum mechanical backlash which still enables stable governing, is 1% of maximum stroke length of the servomotor present in the governor system. To design a system which can achieve the requirements of 1% backlash, a more conventional layout which utilizes links instead of the slots present in the existing governor ring, is suggested.

Research on Acceleration Segmented Compensation Strategy for Backlash of CNC Machine Tools

For the problem of backlash in the semi-closed-loop linear feed servo system of CNC machine tools, which seriously affects the accuracy of machine tools, an acceleration segmentation backlash compensation strategy is proposed. In the reverse motion of the servo motor, the servo motor is controlled to compensate for the backlash error during a period of accelerated motion and a period of decelerated motion. Based on the established backlash transmission model, the parameters of the compensated motion process are calculated. In order to ensure accurate and quick compensation of the gap compensation value for the transmission gap, the backpropagation method is used to backpropagate the acceleration calculation based on whether the acceleration process time is an integer multiple of the servo interpolation period. Finally, the feasibility of the method is verified through experiments, and the results show that the method improves the positioning accuracy of machine tools.

Theoretical analysis of transmission error in rack and pinion systems

Rack and pinion drive systems are widely used in machine tools with long travel distances because the stiffness is independent of the travelled distance, in contrast to other drive systems such as ballscrews. Although the inherent backlash problem of gear systems has been solved by means of utilizing two pinions independently preloaded, the time-varying mesh stiffness causes periodic position differences between the motor encoder and table position, which is known as transmission error, and may lead to vibrations and dynamic load. Few experimental works have analyzed such transmission error, but there are no theoretical approaches in the scientific literature. Therefore, this work aims to first extend previous analytical and approximate equations for mesh stiffness of gearing to rack and pinion systems and validate them with finite element methods. Finally, the effect of geometry variations, such as pressure angle and tooth thickness tolerance, on transmission error is discussed.

A Novel Fuzzy Controller for Visible-Light Camera Using RBF-ANN: Enhanced Positioning and Autofocusing.

To obtain high-precision for focal length fitting and improve the visible-light camera autofocusing speed, simultaneously, the backlash caused by gear gaps is eliminated. We propose an improved RBF (Radical Basis Function) adaptive neural network (ANN) FUZZY PID (Proportional Integral Derivative) position closed-loop control algorithm to achieve the precise positioning of zoom and focus lens groups. Thus, the Levenberg-Marquardt iterative algorithm is used to fit the focal length, and the improved area search algorithm is applied to achieve autofocusing and eliminate backlash. In this paper, we initially adopt an improved RBF ANN fuzzy PID control algorithm in the position closed-loop in the visible-light camera position and velocity double closed-loop control system. Second, a similar triangle method is used to calibrate the focal length of the visible-light camera system, and the Levenberg-Marquardt iterative algorithm is used to fit the relation of the zoom potentiometer code values and the focal length to achieve the zoom position closed-loop control. Finally, the improved area search algorithm is used to achieve fast autofocusing and acquire clear images. The experimental results show that the ITAE (integrated time and absolute error) performance index of the improved RBF ANN fuzzy PID control algorithm is improved by more than two orders of magnitude as compared with the traditional fuzzy PID control algorithm, and the settling time is 6.4 s faster than that of the traditional fuzzy PID control. Then, the Levenberg-Marquardt iterative algorithm has a fast convergence speed, and the fitting precision is high. The quintic polynomial fitting results are basically consistent with the sixth-degree polynomial. The fitting accuracy is much better than that of the quadratic polynomial and exponential. Autofocusing requires less than 2 s and is improved by more than double that of the traditional method. The improved area search algorithm can quickly obtain clear images and solve the backlash problem.

Strut and Ring Connection System Design on External Fixator Based on Hexapod to Increase Bone Flexibility Reconstruction Using Finite Element Analysis List the author names here

An external fixator is a medical device that supports bone reconstruction processes that require correction due to bone deformities. External fixator based on hexapod is the right device to do correction of complex deformities due to its ability to reconstruct bones in three dimensions. There are many external fixator based on hexapod products with varied designs, one of these variations is Taylor spatial frame which uses a universal joint for its connection system. So far, based on U. S. Patent 8,202,273, Taylor spatial frame has a good strut-ring angle (0°) and adjustments. The results of the correction process observations show that the frame has backlash problems due to the clearance between components . This study aims to improve the connection system of the strut and ring of the external fixator so as to produce a range of angles between the strut and the ring which were less than 30 ° with no backlash on its components. The improvements that will be made to the strut and ring connection system use a generic product development process based on Ulrich and Springer and finite element analysis. The results show that there are four alternative improvement concepts that can be produced. One of the four concepts can produce a range of angles between strut and ring for 32.04 °. This research can be useful in the further development of external fixators based on hexapod.

Backlash Compensation for Accurate Control of Biopsy Needle Manipulators having Long Cable Transmission

In the paper, a backlash compensator is proposed for accurate position control of the needle manipulator for the magnetic resonance imaging (MRI) guided biopsy. Having long cable driven transmission, the robot guarantees the MR-compatibility, but has accuracy degradation due to the backlash problem. To handle the problem, a backlash compensator is proposed based on the Prandtl-Ishlinskii model, regarding the continuity of the control input. The particle swarm optimization is used to identify the backlash model. Through the experiments, it is verified that the proposed compensator can reduce the tracking error dramatically, and can provide adequate accuracy for the biopsy operation.

이륜 역진자 로봇의 제어 시스템 개발을 위한 설계 고려사항

This paper addresses some practical design considerations to build a two-wheeled inverted pendulum (TWIP) robot control system. The first issue is to identify the relationship between the primary parameters of the TWIP robot and the guaranteed stability of the time-delayed control loop. Secondly, the required data update rate and the required sensor/actuator performance are suggested for implementing a real-time digital control system. The final issue is concerned with improving the driving performance by investigating the reliability of the inertial sensor for attitude control and the backlash problem in the transmission mechanism.

Energy savings and operation improvement of rotating cement kiln by the implementation of a unique new drive system

Analysis, simulation, implementation and results of a new kiln drive system consisting of two AC motors of 315 kW each, on an existing common tooth gear, as a new contribution for the operational optimisation of rotating kilns, are presented in this study. Two separate inverter units control the two asynchronous motors with a common rectifier. This study also illustrates how backlash problems on tooth gear and maintenance needs are eliminated while reducing operational costs, down-times and energy consumption, by applying contemporary technology, including power electronics and dynamic performance in control systems.

Design of Smart Positioner for a Control Valve to Optimise Backlash Problem

Control valves are an increasingly vital component of modern manufacturing around the world, since control valves are mechanical devices, their performance is less than ideal, and degrades over time. For a plant to perform optimally control valve performance must be tracked and maintained. Backlash is one of much invertible nonlinearity present in control valve, if a valve has some backlash, the loop will have a tendency to oscillate, which will get bigger and bigger as time goes by and will also make the loop slower to respond. At present, pneumatic valve Positioner is used which uses mechanical cam to correct the non-linear nature of control valves. Pneumatic valves Positioner typically are very simple and do not implement integral control. In this project a novel low cost Smart Positioner is designed and developed to improve the performance of control loops. A rotary potentiometer with a linear actuator is used to give feedback signals to the controller of the current position of the control valve. A specially designed control system which is cascade in nature increases the performance of the control system. The Position sensor control being a slave controller acts faster to position the valve and thereby avoiding backlash problem. The developed design is implemented in the Second Order Two Tank Level control system and the performance metrics such as Rise time, Settling time and Steady state errors evaluated found improved after implementing smart Positioner. The oscillation of control valve was found minimum compared to pneumatic Positioner which clearly an indication of reduced backlash in the system. The low cost smart Positioner is RVDT which fixed on a pinion rack and interfacing the proposed second order system using MATLAB for error analysis and LabVIEW software and NI DAQ6008 to run the proposed second order system.

선박/해양플랜트용 FD FAN의 기어식 베인 댐퍼 성능 개선에 관한 연구

ABSTRACT In this study, we developed a gear-type vane damper which replaces the link type through a proper gear design by means of a finite element analysis. We analyzed the fluid flow according to the amount of angular displacement. torque and backlash problems were addressed in conjunction with the pinion as a structural improvement of the forced draft fan (FD FAN). Through an environmental test, . Also, results nearly identical to those in the test could be drawn when using a numerical method. Finally, we compared the gear driving result with simulation results. objective of the present study is to identify a nonlinear flow rate control method for a gear-type vane damper and to propose a damper shape which offers linear flow rate control. This study is related to the development of a gear-type vane damper of the change-link type in a forced draft fan. Key words Marine Forced Draft Fan(선박용 강제통풍휀), Gear Type Vane Damper(기어식 베인 댐퍼), Link Type( ), Vane Shaft( ), Torque( )링크식 베인축 토크

Correction of the concentrated sunlight spot's drift of the IER-UNAM's solar furnace

This paper discusses the methods implemented for the solution of the drift and backlash problems in the heliostat of the High Radiative Flux Solar Furnace recently built at the Renewable Energy Institute (former Center for Energy Research) of the National University of Mexico (IER-UNAM), located at the geographical coordinates 18°50′24″ North latitude and 99°15′00″ West longitude. To solve the observed drift, several algorithms were analyzed for the calculation of the solar vector, and a closed loop through an electronic device (peephole) was implemented which makes corrections to the position of the heliostat. Using the peephole, drift heliostat decreased significantly; 70% in the horizontal direction and 63% in the vertical direction relative to the no use of peephole. The backlash was corrected by means of unbalancing the heliostat.

Third Country Nationals as Euro-Citizens - The Case Defended

The Amsterdam Treaty bolsters Union Citizenship in order to bring the European Union closer to the citizens of Europe . Inadvertently, this strategy gives citizens of non-EU states an inferior status in the European Union, even though they may be semi-permanent residents in a Member State. Union Citizenship increases the social and political exclusion of third country nationals, in violation of the basic democratic principle that those affected by social institutions should also enjoy political levers of influence. The paper first briefly sketches a Liberal Contractualist defense for awarding this group full citizenship in the relevant Member State, arguing in particular for three somewhat contested issues, that: a) third country nationals should not only enjoy Union Citizenship, but also be given national citizenship in the Member State of residence. b) Member states may impose conditions, oaths etc. on such prospective citizens.c) Member States may withhold some privileges from those resident third country nationals who refuse to be naturalised.The paper goes on to present and discuss, only to dismiss, the most plausible arguments offered in defence of current practice within the context of a Europe of open borders for Member State citizens. These arguments seek to deny citizenship to third country nationals in order:a) To protect national and locally endorsed values ensuring social homogeneity of the community;b) To exclude people with non-liberal values;c) To ensure commitment to a shared future which warrants democratic rights in the first place;d) To avoid instability caused by citizens with conflicting multiple loyalties;e) To ensure and foster the ideal of active political participation, impossible for dual citizens;f) To avoid backlash problems among current EU citizens which threaten the stability of welfare policies of Member States and the EU.

Modelling and system identification of a stiff stay wire fence machine

The present paper investigates a severe gear backlash problem encountered in a stiff stay machine that is capable of producing a 26-line fence up to 2.6 m in height at a speed of 80 stays/min. Related problems in the literature typically concentrate on the effect of gear backlash on the ability to control a shaft. However, in this case, very good control of the reference speed of the shaft was maintained in spite of the gear backlash. The problem was that the commanded torques were excessively large and threatened to damage the gearbox. This problem motivated a complete analysis of the system's dynamics including the development of a model to better understand the response and allow the identification of external loads on the system. It was found that the method of sensing the shaft position (resolvers) was a major factor as well as the upgrading of the motor, which was over-responding to disturbances in the shaft. The model was validated using several torque limiting experiments and gave accurate prediction of the machine's major dynamics. The simulation tool developed provides the basis to predict the effect of different loads, wire types, and/or motors on the machine for future designs, minimizing the amount of experimentation on the machine.

Active Damping of Drive Train Oscillations for an Electrically Driven Vehicle

A problem encountered with electrically driven vehicles are resonances in the drive train caused by elasticity and gear play. Disadvantageous effects caused by this are noticeable vibrations and high mechanical stresses due to torque oscillations. The oscillations can be damped using a control structure consisting of a nonlinear observer to estimate the torque in the gear and a controller, which computes a damping torque signal that is added to the driver's demand. The control algorithm was implemented in the existing motor control unit without any additional hardware cost. The controller was successfully tested in a test vehicle. The resonances can essentially be eliminated. The controller copes satisfactorily with the backlash problem.

Effect of nonlinear impact damping on the frequency response of a torsional system with clearance

In this article we examine a particular nonlinear impact damping model that has been well accepted by the scientific community. First, we consider the damping element with a linear spring and examine the nonlinear frequency response characteristics of a torsional system. Second, the impact damping is examined along with the clearance nonlinearity including the backlash problem. Three semi-analytical methods, namely the Describing Function Method, Multi-term Harmonic Balance Method and Stochastic Linearization Method, are utilized to investigate the effect of impact damping. Feasibility of such methods is confirmed by comparing predictions with results yielded by a numerical method. The differences between impact damping and linear viscous damping mechanism are studied in terms of frequency responses, time histories, and the minimum number of harmonics required to simulate the behavior given sinusoidal excitations. Furthermore, the effect of impact damping on sub- and super-harmonic responses and quasi-periodic regimes are examined.

Active Suppression of Torsional Oscillations

A problem with electrically driven vehicles is resonances in the drive train caused by elasticity and gear play. Disadvantageous effects caused by this are noticeable vibrations and high mechanical stresses due to torque oscillations. The oscillations can be damped using a control structure consisting of a nonlinear observer to estimate the torque in the gear and a controller, which computes a damping torque signal that is added to the driver's demand. The control algorithm was implemented in the existing motor control unit without any additional hardware cost. The controller was successfully tested in a test vehicle. The resonances can essentially be eliminated. The controller copes satisfactorily with the backlash problem.

Third Country Nationals as European Citizens: The Case Defended

The Amsterdam Treaty bolsters Union citizenship in order to bring the European Union closer to the citizens of Europe.1Inadvertently, this strategy gives citizens of non-EU states an inferior status in the European Union, even though they may be semi-permanent residents in a Member State. Union citizenship increases the social and political exclusion of third country nationals, in violation of the basic democratic principle that those affected by social institutions should also enjoy political levers of influence. This chapter first briefly sketches a Liberal Contractualist defence for awarding this group full citizenship in the relevant Member State, arguing in particular for three somewhat contested issues: that third country nationals should not only enjoy Union citizenship, but also be given national citizenship in the Member State of residence; that Member States may impose conditions, oaths etc. on such prospective citizens; and that Member States may withhold some privileges from those resident third country nationals who refuse to be naturalised. The chapter goes on to present and discuss, only to dismiss, the most plausible arguments offered in defence of current practice within the context of a Europe of open borders for Member State citizens. These arguments seek to deny citizenship to third country nationals in order to: protect national and locally endorsed values ensuring social homogeneity of the community; exclude people with non-liberal values; ensure commitment to a shared future which warrants democratic rights in the first place; avoid instability caused by citizens with conflicting multiple loyalties; ensure and foster the ideal of active political participation, impossible for dual citizens; and avoid backlash problems among current EU citizens which threaten the stability of welfare policies of member States and the EU.

Design of a linear piezomotor with ultra-high stiffness and nanoprecision

An ultra-stiff nanoprecision linear piezomotor was recently designed for grinding application. This piezomotor consists of three high-voltage piezoelectric actuators integrated by a monolithic flexure frame. This monolithic frame was designed to have multiple functions such as protecting and pre-loading three piezoelectric actuators and withstanding all the shearing forces during operation. The monolithic frame as a motion mechanism eliminates the backlash problem. The stiffness distributions in certain directions over the frame were designed using the finite-element method.

Adaptive control for a class of direct drive robot manipulators

Direct drive robot technology has received considerable attention by the robotics research community given its potential for developing robots with superior positioning accuracy and repeatability characteristics. Direct drive robots do not have the compliance and backlash problems typically associated with geared robots. With the absence of gearing, however, the motors in direct drive robots must be able to produce considerably larger torques than the motors in a geared robot. As a result, the inductances of the motor windings are much larger, thereby making the electrical motor dynamics no longer negligible. In addition, many motors that are ideal for use in direct drive robots are highly non-linear and consequently their dynamics must be included in the overall control design if the benefits of direct drive technologies are to be fully realized. In this paper we design adaptive controllers for a class of direct drive robot manipulators whose actuators consist of Brushed Direct Current (BDC), and Brushless Direct Current (BLDC) and switched reluctance (SR) motors. In particular, the controllers presented handle the multilink dynamics of a rigid link robot and the multiple-input non-linear electrical dynamics of BLDC and SR motors. The result is a class of adaptive controllers that achieve global asymptotic convergence of the link position tracking error in spite of parametric uncertainty throughout the entire electromechanical robot model. In addition, the controllers only require measurements of link position, link velocity and electrical currents.

Adaptive control for a class of direct drive robot manipulators

Direct drive robot technology has received considerable attention by the robotics research community given its potential for developing robots with superior positioning accuracy and repeatability characteristics. Direct drive robots do not have the compliance and backlash problems typically associated with geared robots. With the absence of gearing, however, the motors in direct drive robots must be able to produce considerably larger torques than the motors in a geared robot. As a result, the inductances of the motor windings are much larger, thereby making the electrical motor dynamics no longer negligible. In addition, many motors that are ideal for use in direct drive robots are highly non-linear and consequently their dynamics must be included in the overall control design if the benefits of direct drive technologies are to be fully realized. In this paper we design adaptive controllers for a class of direct drive robot manipulators whose actuators consist of Brushed Direct Current (BDC), and Brushless Direct Current (BLDC) and switched reluctance (SR) motors. In particular, the controllers presented handle the multilink dynamics of a rigid link robot and the multiple-input non-linear electrical dynamics of BLDC and SR motors. The result is a class of adaptive controllers that achieve global asymptotic convergence of the link position tracking error in spite of parametric uncertainty throughout the entire electromechanical robot model. In addition, the controllers only require measurements of link position, link velocity and electrical currents.