Industrial robot arms experience position inaccuracies due to the output cogging torques of the DC servomotors. Therefore, in an attempt to resolve these position problems, an electro-rheological (ER) robotic system is considered as an actuator to drive the robot arm rapidly in both directions. This ER robotic system consists of two ER clutches, an ER brake, a gear train, an encoder and a robot arm. The ER clutches produce clockwise and anti-clockwise rotations. The ER brake decelerates and halts the robot arm. The main aim of this paper is to validate a controller model of the ER robotic arm. Next, a trend study is used to determine the optimum working conditions of the ER actuated-robotic arm. The robotic displacements of both the ER rotary devices and the commercial DC servomotors are compared in terms of position accuracy and speed of response. Finally, the repeatability of the robotic end positions is examined in order to determine the importance of the ER brake.

Aircraft landing gears are subjected to a wide range of excitation conditions, which result in conflicting damping requirements. A novel solution to this problem is to implement semi-active damping using magnetorheological (MR) fluids. This paper presents a design methodology that enables an MR landing gear to be optimized, both in terms of its damping and magnetic circuit performance, whilst adhering to stringent packaging constraints. Such constraints are vital in landing gear, if MR technology is to be considered as feasible in commercial applications. The design approach focuses on the impact or landing phase of an aircraft’s flight, where large variations in sink speed, angle of attack and aircraft mass makes an MR device potentially very attractive. In this study, an equivalent MR model of an existing aircraft landing gear is developed. This includes a dynamic model of an MR shock strut, which accounts for the effects of fluid compressibility. This is important in impulsive loading applications such as landing gear, as fluid compression will reduce device controllability. Using the model, numerical impact simulations are performed to illustrate the performance of the optimized MR shock strut, and hence the effectiveness of the proposed design methodology. Part 2 of this contribution focuses on experimental validation.

Electro-rheological (ER) fluid devices are becoming more popular in the industrial applications. This is due to the fast speed of response and large output dynamics of the ER actuators. The usefulness of this ER dynamic response is considered in the material winding processes where fast output bi-directional responses are essential. Therefore in the present paper, an ER twin clutch mechanism is proposed. This clutch mechanism consists of two identical clutches that rotate in opposite directions. But the bi-directional output dynamics of the clutch mechanism is not well understood due to its non-validation in the past. The main aim of this paper is to model the reciprocating responses of the clutch mechanism and then perform model validation with the measured test results. The close agreements between the modeled and experimental data indicate that the ER output angular velocity and displacement responses’ models of the clutch mechanism are validated. These validated models can then be used to predict accurately the reciprocating output responses of the twin ER clutch mechanism for future research studies.

Aircraft landing gears are subjected to a wide range of excitation conditions with conflicting damping requirements. A novel solution to this problem is to implement semi-active damping using magnetorheological (MR) fluids. In part I of this contribution, a methodology was developed that enables the geometry of a flow mode MR valve to be optimized within the constraints of an existing passive landing gear. The device was designed to be optimal in terms of its impact performance, which was demonstrated using numerical simulations of the complete landing gear system. To perform the simulations, assumptions were made regarding some of the parameters used in the MR shock strut model. In particular, the MR fluid's yield stress, viscosity, and bulk modulus properties were not known accurately. Therefore, the present contribution aims to validate these parameters experimentally, via the manufacture and testing of an MR shock strut. The gas exponent, which is used to model the shock strut's nonlinear stiffness, is also investigated. In general, it is shown that MR fluid property data at high shear rates are required in order to accurately predict performance prior to device manufacture. Furthermore, the study illustrates how fluid compressibility can have a significant influence on the device time constant, and hence on potential control strategies.

Electro-rheological (ER) actuators are potential devices in modern industrial applications. This is due to the excellent performances of the ER devices such as large output dynamics and fast speeds of responses. By using its fast dynamic responses, the ER device or ER brake is studied as a possible actuator to halt the robot arm rapidly. Although many research studies of the ER brake were conducted in the past, but the details of the ER braking dynamics is not clearly understood. Therefore in this paper, a mathematical model is developed and the modelled results are compared with the experimental output velocity responses of the ER brake. After the model validation is completed, the ER brake is subjected to various loads, electric fields, fluid temperatures and volume fractions. By observing the effect of each input variable, the trend behaviour of the ER braking velocity response is investigated in a bid to identify suitable parameters that can halt the robot arm at the fastest time durations. In addition, the braking displacement responses of the attached loads are examined in order to understand the variations of the load position errors at different input conditions. This study is aimed to establish the fundamental knowledge of using the ER brake in future ER-robotic applications.

The main objective here is to eliminate harmonic generation from sensor or actuator systems and to compensate the system losses. If a good model of the system in the time domain is available and the system is time-invariant and continuous, a Volterra series can be constructed by using Associated Linear Equations (ALEs) for both the direct and inverse series. Sensors and actuators such as those designed from the smart technology point of view possess limitations because of non-linear behaviour. A proper Volterra inverse not only eliminates the non-linear behaviour but also compensates the system losses and under appropriate conditions, eliminates transient perturbations of the system allowing more accurate devices with more widespread usage.This work takes advantage of the ALEs to analyse the composition of the pre-inverse and post-inverse Volterra series. The signal is analysed step by step as it passes through the inverse array. Among other characteristics it is found that for certain systems the Volterra inverse can be finite. The effect of the noise on the inverse array performance is also investigated. (c) 2007 Elsevier Ltd. All rights reserved.

Robot arm positioning is an important factor in the robotic process. However, the robot manipulator experiences positioning inaccuracies. This positioning error is due to the dynamic inefficiencies of its actuator: DC servomotor. In a bid to resolve this actuator problem, an electro-rheological (ER) clutch-brake mechanism is employed. This clutch-brake mechanism can actuate and halt the motion of the robot arm. This rotary mechanism consists of two similar clutches that are driven to rotate in the opposite directions and an individual ER brake that provides braking torques to halt the manipulator at the required positions. The main aim of this paper is to establish a control strategy for the ER actuated robot arm by means of model validation with the experimental results. This study is conducted to understand the ER robotic positioning control for future applications.

It is now well established that using actuators, which have faster speeds of response than d.c. servomotors, can solve the positional errors of the robot arms. One of the possible robotic actuators can be an electro-rheological (ER) clutch. To justify this objective, the authors measured the output torque response of a co-axial ER clutch. However, due to the dynamic inefficiency of a torque transducer, the measured torque response is inaccurate for analytical studies. Therefore, this measured torque is signal processed by using the transfer functions of this torque sensor and a filter to yield the ER torque response. The validity of this ER torque is investigated by comparing the numerical errors between the measured torque and its inverse torque response. From the torque error analysis, it is concluded that the ER clutch can be an actuator to improve the positioning accuracies of the robot arms.

Electro-rheological (ER) fluid devices are smart actuators that possess several advantages such as controllable output dynamics and fast speed of response. Due to these output capabilities, an ER clutch is studied for the possibility of actuating the robotic arm. This is achieved by laying a few objectives. The main focus of this paper is to perform model validations of an ER velocity response of this ER clutch. Next, it is aimed to determine a method for rapid energization and de-energization of the ER output velocity for delivering fast start-stop robotic motions. The third aim is to employ the trend study on the ER output velocity response in order to define suitable input parameters for optimum ER robotic performances. The final aim is to determine the reliability of the tested ER fluids shearing in the ER clutch for long-term robotic applications.

In recent years the automotive industry has been working towards intelligent suspension systems that adapt to various road conditions to provide a superior ride and improved road handling. So called semi-active devices, in particular smart fluid dampers, are a viable method of implementing such a system. Despite the fact that magnetorheological (MR) dampers have been used in a number of commercially produced vehicles to date, there is little published information on the control of such devices. Building upon a successful modelling approach developed initially for electrorheological (ER) dampers at the University of Sheffield, a computational model was developed and implemented to simulate the behavior of an MR damper. A proportional force feedback control methodology was adopted and applied to the model with the intention of linearizing the output response. The smart fluid damper is therefore forced to behave in a manner equivalent to a linear damper, with the advantage of having a controllable viscous damping coefficient. Whereas previous research has almost exclusively concentrated upon the controller gain and its influence on the range of linearization which is possible to achieve, this investigation focuses on the time response of the MR fluid and its profound impact on the ability of the control method to linearize the output. Results will be presented which show that the fluid time response introduces a high frequency oscillation into the force/velocity output responses. Simultaneously, at higher excitation frequencies non-linear output responses will be demonstrated. As the fluid time response increases, the oscillations seen at low frequencies reduce but conversely the non-linear output of even moderate excitation frequencies becomes apparent. This result shows the need for a compromise between a larger range of controllability with the introduction of noise at low frequencies, or a smaller, yet noise-free range of controllability. This result may have significance when considered in the wider context of smart fluid applications. The instability and long-term degradation of smart fluids alongside other smart fluid phenomena such as 'in-use fluid thickening' indicate that the fluid time response is apt to change as the fluid is used. With a control system which has been demonstrated to be sensitive to fluid time response this change would of course be detrimental. The authors hope to highlight fluid time response as an important consideration in the design of smart fluid control systems.

Electro-rheological (ER) fluid devices offer controllable output dynamics at fast speed of response. This ER performance is examined for robotic applications. Given the rapid speed of response of the clutch, this ER clutch is considered as an alternative actuator for the robot arm. In the present paper, the main objective is to validate a mathematical model that predicts the output velocity response of this ER device. The other aim is to develop a suitable engineering technique to activate and de-activate the output response of the ER clutch rapidly for achieving fast start-stop motions of ER-actuated robot arm. Next, a trend study on the ER output velocity response is conducted to determine suitable input parameters for fast robotic performances and also to identify some preliminary ER problems for feasible ER-robotic applications.

Electro-rheological (ER) fluids are becoming popular in modern industrial applications. The advantage of employing ER devices is due to the ease of energizing the ER fluids at fast speeds of response. One innovation in ER applications could be in the positioning control of the robotic arm using an ER clutch. In order to actuate the manipulator, the ER output torque response is required. However, the behaviour of this ER torque response at different input conditions is not clearly understood. Therefore, in this paper, a sample study of the ER output torque is conducted. The ER output torque responses at different input parameters are studied carefully for the establishment of an appropriate ER transfer function in shear mode. This transfer function will serve as an important feature in future ER-actuated robot arm's control process.

Recent research into the use of thermal barrier coatings has shown that they can provide sufficient additional damping, reducing vibration levels and significantly extending the life of the coated component.Various deposition techniques may be employed to apply ceramic coatings with Air Plasma Spraying (APS) and Electron Beam - Physical Vapour Deposition (EB-PVD) being the most widely used. However, one has to take into account that even when the starting ceramic material is the same, the microstructures of the resultant coatings depend strongly on the deposition technique.The objective of this paper is to study of the differences in the damping behaviour and stiffness of an yttria-stabilised zirconia (YSZ with 8%wt yttria) coating deposited by APS and by EB-PVD. Both damping and stiffness of these two YSZ coatings were estimated from tests performed at room and high temperatures. Moreover, this paper presents the microstructural characterisation of these two YSZ coatings using scanning electron microscopy, and attempts a correlation of the differences in their properties to their microstructure.

Flexibility and speed of response are two key requirements in the design of machinery for high-speed manufacturing operations. These two requirements are often conflicting and their resolution requires considerable ingenuity on the part of the designer. A novel actuator based upon the use of twin electro-rheological (ER) clutches is described together with its modification to control the motion (angular displacement, angular velocity) of a robot manipulator arm. The development of a new experimental facility involving the robot manipulator arm is described. In the basic twin ER clutch facility, the motion of a toothed belt is controlled by manipulating the electric field applied to each ER clutch. The belt, in turn, controls the angular position and velocity of the robot arm. The use of twin clutches allows motion to be imparted in opposite directions without the need for return springs or similar mechanisms. To improve the positional performance an ER brake is added to the robot arm mechanism. The extension to the dynamic model for the ER clutch mechanism to incorporate the robot arm and ER brake is outlined and is validated experimentally. The displacement response of the robot arm is then examined as a trend study using different motor driving speeds. The positional accuracy of the robot arm and its repeatability is then demonstrated.

Previous work has demonstrated that if a system possesses a Volterra series representation, it can be described by a series of associated linear equations (ALEs). Each ALE produces a particular Volterra operator. The versatility of this methodology allows the independent observation of each harmonic order component in the system response. In the frequency domain the associated frequency response functions (AFRFs) are shown to be easier to analyse and interpret than the more complicated higher-order frequency response functions (HFRFs). Based on a single bi-dimensional graph a full analysis of the system's harmonic behaviour is carried out for the single degree of freedom (sdof) case.

Non-linear time-invariant systems may be sometimes represented in the time-domain by a Volterra series which is a non-parametric, time-domain representation, or in the frequency-domain by the so-called higher-order frequency response functions (HFRFs). A non-parametric model in the time-domain gives very little insight into the intimate details of the non-linear system. Conversely the HFRFs are complicated in shape and are difficult to analyse. The graphical display of the HFRFs has the disadvantage of been multidimensional. It is known that the nth-order Volterra operator is a multi-linear-function of a combination of input signals. In fact, Hammerstein and Duffing type systems possess a linear relationship between the nth-order Volterra operator response and inputs composed of a combination of lower-order Volterra operators. This characteristic is used here to model the behaviour of the Volterra operators by linear equations that map the nth-order operator from an excitation of the same order produced by a combination of lower-order operators. This group of equations is referred to here as the Associated Linear Equations (ALEs). These ALEs can be used in simulation, control and as an analytical tool for the Volterra class of non-linear systems. The main advantage is that theory that up to today has been limited to linear systems can be used on this kind of non-linear systems allowing simpler manipulations.

This paper describes progress on a new technique to detect pipeline features and leaks using signal processing of a pressure wave measurement. Previous work (by the present authors) has shown that the analysis of pressure wave reflections in fluid pipe networks can be used to identify specific pipeline features such as open ends, closed ends, valves, junctions, and certain types of bends. It was demonstrated that by using an extension of cross-correlation analysis, the identification of features can be achieved using fewer sensors than are traditionally employed. The key to the effectiveness of the technique lies in the artificial generation of pressure waves using a solenoid valve, rather than relying upon natural sources of fluid excitation. This paper uses an enhanced signal processing technique to improve the detection of leaks. It is shown experimentally that features and leaks can be detected around a sharp bend and up to seven reflections from features/leaks can be detected, by which time the wave has traveled over 95 m. The testing determined the position of a leak to within an accuracy of 5%, even when the location of the reflection from a leak is itself dispersed over a certain distance and, therefore, does not cause an exact reflection of the wave.

The orifice plate flow meter is the most common form of differential pressure flow meter used in industry. The standard discharge coefficient, which is defined by both British Standard and ISO 5167, is only valid if the flow approaching the meter is perfectly settled and fully developed. However, in practical applications the flow approaching the orifice meter is often disturbed by pipe-fittings and consequently the measurements become inaccurate. Basically, the design of the orifice plate meters that are independent of the upstream disturbances is a main goal for orifice plate metering. This task can be achieved either by using a long straight settling length upstream and downstream of the orifice plate or using a flow conditioner upstream of an orifice plate. In addition, the standard orifice plate is vulnerable when metering dirty flow due to the accumulation of dirt in front of the orifice plate which can alter the accuracy of metering as well. In this paper the effect of the swirler flow conditioner for both standard and non-standard flow conditions has been investigated in an experimental rig and validation of the results has been justified with the appropriate CFD domains. In these investigations the effect of different designs of swirler flow conditioners have been examined in asymmetric and swirling flow profiles. The results so far show the cone swirler flow conditioner has a desirable effect for both asymmetric and swirling flow disturbances. They also show the error of metering for non-standard velocity profiles with the swirler flow conditioner is typically 1.5% compared to around 4% for a standard orifice plate. Moreover using a swirler conditioner tends to keep particles in suspension and thus prevents the accumulation of dirt particles in front of orifice plate. All experimental and numerical results here are presented for different velocity profiles both swirling and asymmetric profiles, mass flow rates and for beta=0.5.

Magnetorheological (MR) fluids provide a novel solution to adapt damping levels in aircraft landing gear, so that optimal performance can be achieved over a wide range of conditions. The present study helps to demonstrate the feasibility of this solution by sizing an MR valve within the constraints of an existing commercial (passive) oleopneumatic shock strut. Previous work on MR landing gear has tended to focus on potential control strategies rather than design and sizing issues. However these latter aspects are of great importance in aircraft systems, where space and weight are vital design constraints. To aid the sizing analysis performed in this study, accurate quasi-steady and dynamic impact models of passive and MR oleopneumatic landing gears are developed. The model is validated against experimental data incorporating the passive device, which is then used as a benchmark for the MR designs and to assess fail safety. The dynamic model is particularly important as it incorporates fluid compressibility, which may be a significant contributor to the overall response of the device in an impact scenario. The present study also aims to give further insight into high velocity MR valve flow, which will be inevitable during impulsive loading. This area remains largely unexplored and particular importance is given to valve Reynolds number since turbulent values are known to reduce device performance. The feasibility of an MR landing gear will be largely dependant on these factors.