Improving Turret Control on Military Vehicles

Recent additions of armor have made light tactical vehicle turrets heavy enough that mechanical assistance is required for them to rotate. The Army’s solution is the Battery Powered Motorized Traversing Unit (BPMTU) which uses a joystick to traverse the turret. Use of the joystick distracts the gunner and prevents the gunner from continuously engaging the target while rotating the turret. This paper presents a modification to the weapon mount that allows the turret to be controlled by the position of the weapon itself and emphasizes the design process used to develop the inovation. With this design, the gunner can now maintain contact with a target, while rotating the turret, without fiddling with the joystick. The Weapon Activated and Controlled Turret (WACT) consists of two primary components; the bottom component is stationary relative to the turret and contains a Hall effect sensor and the top component rotates with the weapon and holds a linear magnet. As the position of the sensor relative to the magnet changes, the corresponding strength of the magnetic field also varies. This change in magnetic force induces a similar response in the output voltage of the Hall effect sensor, effectively translating rotational motion into an electric signal able to control the turret motor.

Dynamic Antiplane Interaction of Subsurface Circular Cavities in a Semi-Infinite Piezoelectric Medium

In the present work, dynamic interaction is investigated theoretically between several circular cavities near the surface in a semi-infinite piezoelectric medium subjected to time-harmonic incident anti-plane shearing. The analyses are based upon the use of complex variable and multi coordinates. Dynamic stress concentration factors at the edges of the subsurface circular cavities are obtained by solving boundary value problems with the method of orthogonal function expansion. Some numerical solutions about two interacting subsurface circular cavities in a semi-infinite piezoelectric medium are plotted so as to show how the frequencies of incident wave, the piezoelectric characteristic parameters of the material and the structural geometries influence on the dynamic stress concentration factors.

Control of a Robotic UV Curing Process With Thermal Vision Feedback Through Two IR Cameras

Robotic ultra-violet (UV) curing is considered to be one of the effective ways to replace the current convection-based methods in various manufacturing processes due to its fast curing rate and high energy efficiency. This paper presents a closed-loop control of a robotic UV curing system by using thermal vision feedback through two infrared (IR) cameras. The proposed approach is developed based on a mathematical analysis of the fundamental UV curing process and the integration of the local and global IR cameras in a cascade manner. A computer simulation study is conducted to evaluate the proposed strategy by regarding two control variables: the radiant intensity of the UV heater and the sweeping speed of the robot end effector. The results indicate that controllers using either control variable can compensate for interferences and improve curing quality under this thermal-vision-based architecture.

Flight Characteristics of Flapping Wing Miniature Air Vehicles With “Figure-8” Spherical Motion

Hummingbirds and some insects exhibit “Figure-8” flapping motion that allows them to go through a variety of maneuvers including hovering. Understanding the flight characteristics of Figure-8 flapping motion can potentially yield the foundation of flapping wing UAVs that can experience similar maneuverability. In this paper, a mathematical model of the dynamic and aerodynamic forces associated with Figure-8 motion generated by a spherical four bar mechanism is developed. For validation, a FWMAV prototype with the wing attached to a coupler point and driven by a DC servo motor is created for experimental testing. Wind tunnel testing is conducted to determine the coefficients of flight and the effects of dynamic stall. The wing is driven at speeds up to 12.25 Hz with results compared to that of the model. The results indicate good correlation between mathematical model and experimental prototype.

Modified PD Control of Rotary Inverted Pendulum

The inverted pendulum, a classical mechatronic application, exists in many different forms. In despite that many works have been done to balance the pendulum link on end of this device using feedback control but few studies have been developed to control this rotary inverted pendulum using PD controller. In classical methods, using PD, PI or PID control, difficulties appear due to one of the coefficients becomes zero in closed loop transfer function denominator and consequently the system becomes unstable. In this study, an arbitrary pole is placed in order to create a break point in root locus, so by this way a PD controller can be designed for this new system. Also, disturbance rejection has been investigated by state space method in this paper. The results of this modified PD controller are compared with full state feedback control and optimal control, so the method used in this study has been validated.

Dynamics of Pipes Conveying Fluid With a Non-Uniform Velocity Profile

Previous work on stability of fluid-conveying cantilever pipes assumed a uniform velocity profile for the conveyed fluid. In real fluid flows, the presence of viscosity leads to a sheared region near the wall. Earlier studies correctly note that viscous forces drop out of the system’s dynamics since the force of fluid shear on the wall is precisely balanced by pressure drop in the conveyed fluid. The effect of shear has therefore not been ignored in these studies. However, a uniform velocity profile assumes that the sheared region is infinitely thin. Prior analysis was extended to account for a fully developed non-uniform profile such as would be encountered in real fluid flows. A modified equation of motion was derived to account for the reduced momentum carried by the sheared fluid. Numerical analysis was carried out to determine a number of velocity profiles over the Reynolds number range of interest and a simple set of curve fits was used when finer discretization was required. Stability analysis of a pipe conveying fluid with these profiles was performed, and the results were compared to a uniform profile. The mass ratio, β, is the ratio of the fluid mass to the total system mass. At β = 0.2, the non-uniform case becomes unstable at a critical velocity, ucr, that is 5.4% lower than the uniform case. The critical frequency, fcr, is 0.36% higher than the uniform case. A more sensitive region exists near β = 0.32. There, the nonuniform velocity ucr is 23% lower than the uniform case and the non-uniform critical frequency fcr is 49% of the uniform case.

Imperfection Sensitivity of Compressed Circular Cylindrical Shells Under Periodic Axial Loads

In the present paper the dynamic stability of circular cylindrical shells is investigated; the combined effect of compressive static and periodic axial loads is considered. The Sanders-Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration; Lagrange equations are used to reduce the nonlinear partial differential equations to a set of ordinary differential equations. The dynamic stability is investigated using direct numerical simulation and a dichotomic algorithm to find the instability boundaries as the excitation frequency is varied; the effect of geometric imperfections is investigated in detail. The accuracy of the approach is checked by means of comparisons with the literature.

Motion Performance Analysis of Double-Cylinder Parallel Manipulators

Double-cylinder parallel manipulators are closed-loop two-degree-of-freedom linkages. They are preferred to use because of their simplicity plus the common advantages of parallel manipulators such as high stiffness, load-bearing, operation speed and precision positioning. Like other parallel manipulators, the output motion of double-cylinder parallel manipulators is not as flexible as two-degree-of-freedom serial manipulators. The motion performance analysis plays a critical role for this type of parallel manipulator to be applied successfully. In this paper, the linkage feasibility conditions are established based on the transmission angle. When feasibility conditions are satisfied, there is no dead position during operation. The workspace is generated by using curve-enveloping theory. The singularity characteristics are analyzed within the workspace. The motion performance index contours within the workspace are produced using the condition number of the manipulator Jacobian matrix. The results of this paper provide guidelines to apply this type of parallel manipulator.

A Nonlinear Signal Analysis Scheme for Localization of a Moving Acoustic Source

The synthesis of coupled systems including linear propagation media and nonlinear lumped subsystems is investigated. The resulting coupled system is expected to exhibit improved dynamic behavior. Such improvements are sought after by designing exclusively the lumped nonlinear subsystem and not by modifying the propagation medium. The lumped subsystem can be static or dynamic as well as passive or active. The design method is based on the Volterra-Wiener theory of nonlinear systems combined with the Linear Fractional Transformation employed for the analysis of uncertain linear systems. Although the techniques are applicable to a variety of practical engineering and physical systems, this work addresses acoustic source localization. Indeed, a moving acoustic source can be considered to nonlinearly modify the characteristics of a carrier acoustic wave. Such an acoustic carrier might be a monochromatic or polychromatic tone as well as other broadband signals such as band-limited white or colored noise. The sound source position signal is propagated through a nonlinear operator and then, under noise-free environment assumptions, determines the sound pressure level at the receiver location. In this paper, the proposed method is applied to the simplified case of a one-dimensional acoustic cavity defined by totally reflective barriers. Furthermore, the lossless wave equation is assumed to govern the sound pressure level in the homogeneous domain of interest. However, even in this simple scenario, only the additional assumptions of negligible source velocity and acceleration allow the derivation of an expression for the sound pressure level containing exclusively source displacement. In this context, simulation data series or analytical solutions, approximate or exact, are post-processed in order to determine the Volterra kernels, which effectively are a convenient extension of the impulse response concept in the nonlinear case, of the operator connecting source displacement to sound pressure level at the receiver. The outcome is Linear Time Invariant models depicting the dominant sound propagation dynamics. Then the synthesis stage is based on the properties of interconnected nonlinear systems that are described in the Volterra-Wiener framework. By using such properties, the signal processing algorithm for the estimation of the acoustic source position based on the received sound pressure level is finally developed.

Modeling of a Hydraulic Elevator Driven by an Open-Loop Control

Electro-hydraulic elevators are widely used systems, especially in low level buildings, due to their very good ratio between power generation and dynamic response. Generally, the goal of an elevator system is just to reach the floor with a precision enough to be comfortable for the passengers, without the need to follow a specific law of motion; hence an open-loop control system could be enough. Otherwise such a kind of solution reduces the number of components, bringing down the costs of production. On the other hand a complete knowledge of the mechanical system’s behaviour is required. In this work we deal with the analysis of the behaviour of a commercial hydraulic elevator driven by an open loop control that monitors the downstream pressure of the proportional valve supplying the cylinder. At the end of the paper, a closed loop solution based on the pressure measurement and on the motion time is proposed.