Applied Mechanics and Materials Vol. 761

Abstract: This paper investigates the effectiveness of piezostack actuator in attenuating the frequency dependent excited vibration of a suspended handle. A shaker is used to produce a base excitation to the suspended handle and a piezostack actuator is used to generate the vibration cancellation for the handle. The investigation covers vibration operating frequency from 50 to 500 Hz. This study also looked at the initial performance of piezostack actuator for the AVC system. A PID controller is design to generate the counter voltage for the piezostack actuator to attenuate the vibration of the handle. The results show that the highest vibration attenuation of the suspended handle occurred at operating frequency of 450 Hz with 90 % of vibration attenuation and the lowest at 50 Hz with 2.4 % of vibration attenuation.

Abstract: The study of humanoid robot locomotion has been focusing on the development of walking pattern generation. However, the robot has the possibility of slipping on the ground due to the simultaneous occurrence of translational and rotational motions as a robot is walking. Technically, both issues disrupt the walking straightness of the robot. This study investigates the influence of the robot swing arms posture with a modified walking pattern generation to minimize the problem. Simulations were done by preparing 10 different elbow joint angles with swing arms and each one of them were tested with the same value of Maximum Lifting Height, H. The analysis was done by collecting the data from the Global Positional Sensor (GPS) from the robot and calculating the Root Mean Square Error (RMSE) to determine which variable has the lowest percentage of RMSE. The angular velocity graph was used to analyze the deviation encountered by the robot while walking by determining the average of angular velocity. The results showed that the arm posture of the robot does influence its walking straightness in a small amount.

Abstract: This paper presents the modelling and analysis of path-following planning motion of an All-Terrain Vehicle (ATV) using system identification technique in term of yaw stability. The modelling is based on the single track and established by using Newtonian equation motion. Mathematical modelling is constructed in form of state space equation with the parameters used are measured through physical measurement of prototype ATV. Based on this model selection, the open loop system is simulated and the result will be validated by using system identification. Inertial Measurement Unit (IMU) sensor is used to collect and measure the data for the path-following planning. The analysis results for yaw stability of prototype ATV are validated by system identification method with step response approach. Both of the simulated and measured data is compared and the data is estimated to get the best fit for yaw estimation by using complimentary filter technique. From the result, the best fit for yaw estimation is 91.96% and considered as stabilized at steering angle of 45°.

Abstract: The control of rotary inverted pendulum is a case of classical robust controller design of non-linear system applications. In the control system design, a precise system model is a pre-requisite for an enhanced and optimum control performance. This paper describes the dynamic system model of an inverted pendulum system. The mathematical model was derived, linearized at the upright equilibrium points and validated using non-linear least square frequency domain identification approach based on measured frequency response function of the physical system. Besides that, a linear quadratic regulator (LQR) controller was designed as the balancing controller for the pendulum. An extensive analysis was performed on the effect of the weighting parameter Q on the static time of arm, balance time of pendulum, oscillation, as well as, response of arm and pendulum, in order to determine the optimum state-feedback control vector, K. Furthermore, the optimum control vector was successfully applied and validated on the physical system to stabilize the pendulum in its upright position. In the experimental validation, the LQR controller was able to keep the pendulum in its upright position even in the presence of external disturbance forces.

Abstract: Two types of rotary motion electrostatic actuators were designed and analyzed using Finite Element Method (FEM) analysis. This paper discussed the comparisons and detailed thrust force analysis of the two actuators. Both designs have similar specifications; i.e the number of rotor’s teeth to stator’s teeth ratio, radius and thickness of rotor, and gap between stator and rotor. Two structures were designed & evaluated; (a) Side-Driven Electrostatic Actuator and (b) Bottom-Driven Electrostatic Actuator. The paper focuses on comparing & analyzing the generated electrostatic thrust force for both designs when the electrostatic actuator’s parameters are varied. Ansys Maxwell 3D software is used to design and analyze the generated thrust force of the two rotary motion electrostatic actuators. The FEM analyses have been carried out by (i) varying the actuator size; (ii), varying the actuator thickness and (iii) varying the actuator teeth ratio. The FEM analysis shows that the Bottom-Drive Electrostatic Actuator exhibit greater thrust force, 4931.80μN compared to the Side-Drive Electrostatic Actuator, 240.96μN; when the actuator’s radius is 700μm, thickness is 50μm, gap between the stator and rotor is 2μm and the teeth ratio is 16:12.

Abstract: In this paper, a construction of a prototype to represent passive vehicle suspension system for quarter car model is considered. The prototype is represented by two degree-of freedom quarter-car model which are conventionally used by researchers. This laboratory equipment is developed in order to familiarize students with 2 DoF passive suspension system model. It consists of two masses, two springs and a damper. This equipment is easily dismantled and could be assembled with different spring and damper constants which contribute to different characteristics of the suspension system. A number of experiments have been carried out using the experiment setup in order to identify the suspension system characteristics i.e. experiments with different vehicle body mass, different period for one pulse and different pulse width of input pressure of the road excitation have been conducted. The experiment results are evaluated based on the vehicle body displacement and tire displacement of the prototype. Experiment results show that the pulse width of the input pressure or road profile is directly affected the characteristic of this passive suspension system. Lastly, simulations were done in order to compare the simulation and experimental results.

Abstract: This paper presents the development of the system identification (SI) for the highly nonlinear piezoelectric patch actuator. The transfer function is determined by using the nonlinear least square (NLS) method after the direct measurements of input-output data are taken from the actuator that is installed on a well-equipped platform. The results were validated to ensure that the transfer function derived fits well with the experimental output.

Abstract: This paper reviews compensation methods on effects of disturbance forces on positioning accuracy in linear drives system for machine tools applications. Linear motor is directly subjected to disturbances forces acting in the direction of motion giving rise to the needs for alternative robust controllers in order to ensure precision and high tracking performance. This paper investigates effect of cutting forces generated during milling process on tracking accuracy of a linear drive motor. Recent studies are focusing on design of adaptive compensators that provide robustness against system uncertainties while maintaining high degree of precision and accuracy generally required in high performance machining applications.

Abstract: This paper presents an experimental study of wear mechanism on high speed milling of FC300 gray cast iron using TiAlN coated carbide cutting tool. The experiment was carried out under dry cutting condition with different cutting speed (95-143m/min) and feed rate (4000-7000 mm/min). The cutting tool for machining FC300 gray cast iron is a ball nose end mill ø32 mm coated with TiAlN. Wear mechanism was analyzed at VB 0.08mm after 60 minute machining. The flank wear increased when the spindle speed and feed rate increased caused by the generated high shearing force and high cutting temperature. The dominant wear mechanisms appear to be the abrasion, adhesion, chipping and delaminating of coating at the contact surface of cutting tool. Formation of built-up edge (BUE) was evidence for most of the cutting trials.

Abstract: This paper aims to study the tool life of coated and uncoated high speed steel (HSS) when machining LM6 aluminium. The experiment was carried out in dry condition with spindle speed of 5000 rpm and 6000 rpm, and feed rate of 90 mm/min and 120 mm/min. Axial and radial depth of cut remain constant at 0.5 mm and 1.0 mm, respectively during the experiment. Throughout the experiments, coated HSS showed higher tool life as compared to uncoated HSS due to the coating layer of titanium aluminium nitride (TiAlN) provides protection from rapid wear during machining. For both cutting tools, the optimum cutting parameter was recorded at 5000 rpm spindle speed, 90 mm/min feed rate, 0.5 mm axial depth of cut and 1.0 mm radial depth of cut. Some evidence of built up edge (BUE) formation were observed at most of cutting tools, showing the dominant wear mechanisms appear to be adhesive wear.