Experimental investigation of feedforward control schemes of a flexible robot manipulator system

This paper presents experimental investigations into the applications of feedforward control schemes for vibration control of a flexible manipulator system. Feedforward control schemes based on input shaping and filtering techniques are to be examined. A constrained planar single-link flexible manipulator is considered in this experimental work. An unshaped bang-bang torque input is used to determine the characteristic parameters of the system for design and evaluation of the input shaping control techniques. The input shapers and filtering techniques are designed based on the properties of the system. Simulation results of the response of the manipulator to the shaped and filtered inputs are presented in time and frequency domains. Performances of the shapers are examined in terms of level of vibration reduction and time response specifications. The effects of derivative order of the input shaper on the performance of the system are investigated. Finally, a comparative assessment of the control strategies is presented and discusse

MONETARY POLICY EFFECTIVENESS & YIELD CURVE DYNAMICS – US EXPERIENCE FROM AHETEREGENEOUS ECONOMIC PERSPECTIVE (2000-2009)

The question of how do the monetary policy translate across the yield curve remain at the forefront of many recent policy debates. The monetary policy targets the very short end of the yield curve although real economic activity is largely dependent upon the medium to long- term market interest rates. Conventional wisdom agree that given efficient market conditions decrease in the monetary policy target rate leads to an immediate decrease in market interest rates, and an increase in bond prices; yet evidence for this view is elusive. Bringing the foundations of Expectation Hypothesis (EH) and empirical analysis of US money market and government bond daily yield rates for the period 2000 to 2009 explains that monetary policy impact monotonically decreases over the yield curve. The impact appears to be waning at a faster pace and concentrate on a preferred habitat towards shorter end at times of financial and economic uncertainties compared against stable economic period. This invites policy attention, especially at times of economic uncertainty, on the part of monetary policy effectiveness and market confidence in US to resurrect economic activities.Monetary policy; Expectation hypothesis; Segmented market hypothesis; Preferred habitat hypothesis; Yield curve and term structure of interest rates

Hybrid iterative learning control of a flexible manipulator

This paper presents an investigation into the development of a hybrid control scheme with iterative learning for input tracking and end-point vibration suppression of a flexible manipulator system. The dynamic model of the system is derived using the finite element method. Initially, a collocated proportional-derivative (PD) controller using hub angle and hub velocity feedback is developed for control of rigid-body motion of the system. This is then extended to incorporate a non-collocated proportional-integral-derivative (PID) controller with iterative learning for control of vibration of the system. Simulation results of the response of the manipulator with the controllers are presented in the time and frequency domains. The performance of the hybrid iterative learning control scheme is assessed in terms of input tracking and level of vibration reduction in comparison to a conventionally designed PD-PID control scheme. The effectiveness of the control scheme in handling various payloads is also studied

Mo (VI)/ZrO2 coated on honeycomb monolith as solid acid green catalyst for the acetylation of substituted alcohols and amines under solvent free conditions

553-561Honeycomb (HC) monolith coated with solid acids such as Mo (VI)/ZrO2 (MZ) with different Mo loadings (2, 6 and 10%) have been prepared by wet impregnation method and characterized by NH3 –TPD, BET surface area, PXRD, ICP-OES, SEM, TEM and EDAX techniques. These catalysts have been used as for the synthesis of O and N-acetylation reactions by the condensation of various alcohols with acetic anhydride under solvent free conditions in shorter times (20 min) at moderate temperature (70°C). Especially, 6% Mo (VI)/ZrO2 catalysts are found to be highly acidic and also resulted in high yields of O and N acetylated products up to ~99%. This methodology offers several advantages such as excellent yields, easy procedure, mild and environmentally benign conditions. MZ catalysts are found to be economical, efficient and highly active, recyclable and reusable up to 6 reaction cycles without much loss of their activity

System Identification and LMI Based Robust PID Control of a Two-Link Flexible Manipulator

This paper presents investigations into the development of a linear matrix inequalities (LMI) based robust PID control of a nonlinear Two-Link Flexible Manipulator (TLFM) incorporating payload. A set of linear models of a TLFM is obtained by using system identification method in which the linear model represents the operating ranges of the dynamic system. Thus, the LMI constraints permit to robustly guarantee a certain perturbation rejection level and a region of pole location.  To study the effectiveness of the controller, initially a PID control is developed for TLFM with varying payloads. The performances of the controllers are assessed in terms of the input tracking controller capability of the system as compared to the response with PID control. Moreover, the robustness of the LMI based robust PID control schemes is discussed. Finally, a comparative assessment of the control strategies is presented

Morphological Characteristics of Hardened Cement Pastes Incorporating Nano-palm Oil Fuel Ash

Recently, nano-sized additives and supplementary cementing materials (SCM) have shown to improve the mechanical and durability of mortars and concretes. This study investigates the incorporation of nano-POFA (nPOFA) into cement paste so as to observe its effect towards the microstructure development of cement. Additionally, the effect of micro-sized POFA (mPOFA) was also carried out for comparison. The mPOFA were subjected to milling for the generation of nPOFA. The prepared nPOFA exhibited a BET specific surface area of 145.35 m2/g with an average particle size ranging between 20 nm to 90 nm. Cement pastes were prepared with 10% - 50% replacement of nPOFA and 10% - 30% replacement of mPOFA. The morphological analysis of hardened cement paste (hcp) containing nPOFA (nPOFA-hcp), mPOFA (mPOFA-hcp) at the curing ages of 7, 28 and 90 days were conducted and compared with Ordinary Portland cement paste. At 7 days curing, the nPOFA particles acted as fillers and nucleation sites to accelerate cement hydration. The nPOFA particles reduced the appearance of lime crystals in the nPOFA-hcp at later curing ages due to the occurrence of pozzolanic reactions which formed secondary calcium-silicate-hydrates gel, resulting in a compact microstructure. The study concluded that the nPOFA particles created a dense and closely-packed microstructure of the hardened cement pastes due to the filling effect and pozzolanic reactions in the pastes

Sensor Fusion Algorithm by Complementary Filter for Attitude Estimation of Quadrotor with Low-Cost IMU

This paper proposes a sensor fusion algorithm by complementary filter technique for attitude estimation of quadrotor UAV using low-cost MEMS IMU. Angular rate from gyroscope tend to drift over a time while accelerometer data is commonly effected with environmental noise. Therefore, high frequency gyroscope signal and low frequency accelerometer signal is fused using complementary filter algorithm. The complementary filter scaling factor K1=0.98 and K2=0.02 are used to merge both gyro and accelerometer. The results show that the smooth roll, pitch and yaw attitude angle can be obtained from the low cost IMU by using proposed sensor fusion algorithm

Sliding mode control for altitude and attitude stabilization of quadrotor UAV with external disturbance

This paper addresses the problem of robust altitude and attitude control of ‘×’ mode configuration quadrotor UAV using Lyapunov stability based sliding mode control with saturation function. The dynamic model of the quadrotor was derived by considering nonlinearity factor. MATLAB Simulink was used to simulate the model in two different conditions; without and with the presence of external disturbance. This was done to test the robustness of the control method. Simulation results showed that the sliding mode controller provides good performance and robustness against disturbance

Effect of FSW Parameters on The Microstructure and Mechanical Properties of T-joints between Dissimilar Al-Alloys

The main purpose of this research is to develop T-joints between the aluminum AA 2024-T4 and AA 7075-T6 using friction stir welding.  The effect of tool geometries, tool traveling speed, and rotational rate in the welded T-joints were investigated and discussed. Three different tools were used with different shoulder to pin ratios 3.28, 3.36, and 4.31. After optimization, the best tool dimension has used with the different rotational and welding speeds. Three tool traverse speeds of 50, 75, and 100 mm/min were used. Two rotation rates of 800 rpm and 1000 rpm were applied. After FSW, at a number of the above FSW parameters' combinations, macrostructure and microstructure analyses were done using optical microscopy. In order to have an insight into the mechanical properties, hardness measurements and tensile testing were carried out. Using small shoulder to pin ratio produced visually unacceptable T-joint. Opposite happened by using the tool with 4.31 of shoulder to pin ratio. Furthermore, the results showed sound T-welds with no obvious defects at high rotational rate of 1000 rpm with the two used traveling speeds. Asymmetric temperature distribution was observed between the two sides, advance side (AS) and retreating side (RS