Papers by Keyword: Equation of Motion

Abstract: In the field of impact engineering, high-speed impact phenomena are simulated using a projectile accelerator. At the Impact Engineering Laboratory in Ritsumeikan University, a single-stage gas gun was designed to investigate the high-speed penetration phenomena of impacts in sand, which is known to show fluid-like behavior. The gas gun consists of a 2 m launch tube that can achieve projectile muzzle velocities of up to around 500 m/s. The theoretical muzzle velocity of the projectile can be calculated by considering the speed of sound and the specific heat ratio of propellant gases. A performance evaluation for high-pressure ranges of 1 MPa and higher in a high-pressure vessel has been conducted. When fitting parameters are introduced to the theoretical formula, good agreement is obtained with the experimental results. In this study, experiments for low pressure ranges were conducted to predict the projectile velocity and to investigate the minimum velocity limit of the projectile. By introducing fitting parameters to the theoretical formula, the projectile velocity could be predicted accurately for pressure ranges less than 1 MPa. Furthermore, the minimum velocity limit of this equipment was found to be around 30 m/s.

Abstract: An airdrop model with aerial carrier is carried out to simulate an airdrop test. A coupled CFD/6 DOF is designed to compute the orientation and trajectory of the airdrop model. The results show that the CFD/6 DOF coupled method is appropriate to simulate this problem with a sufficient precision. The airdrop’s motion is strongly coupled with the aerodynamic force after leaving the sliding rail and the trajectory of its CG is mainly in the symmetry of the aerial carrier. The variation of its orientation mainly rolls in X axis direction and it swings as an approximate periodic oscillation which amplitude decreases over time. The maximum angle of orientation in X axis direction is-116°in 5 seconds. The similar variation of the airdrop motion is present in different angle of attack and sideslip of the aerial carrier.

Abstract: According to the technology requirement and existing problems of the key working parts (punching device) of the peanut mulching film and punching planter, the punching device of the peanut mulching film and punching planter was designed adapt to first mulching film and then sowing. It was introduced the structure and working principle of the punching device, and the punching mechanism are studied. The trajectory of the punching parts was analyzed in the punching process, and the parameter equation of the punching profile was established. On the basis, the main structure parameters of the punching device were analyzed and optimized. The study provides reference and basis for the design and development of the peanut mulching film and punching planter.

Abstract: The purpose of this study is to propose a new quadruped walking machine and investigate its dynamics. This paper first proposes a new quadruped walking machine and introduces its structure. The basic theory behind the equation of motion is briefly introduced. The dynamic characteristics of the walking machine, including the position, velocity, acceleration, support leg sequence, foot trajectory and pitch angle, are investigated and compared with the existing design. The results show that better transmission efficiency is achieved when the driving torque of the walking machine acts on the shaft of the crank. Compared to the existing design, the design proposed in this study has fewer changes in pitch angle during movement and exhibits less skidding while changing support leg.

Abstract: This paper takes the spindle of inner cavity shaping machine tool as the research object, analyzes the spindle structure of the machine tool and establishes the equations of motion, analyzes the influence that the spindle speed and tool deflection speed have on the tool rotary speed using Matlab and ADAMS, determines the allowed deflection range of the tool, sets up the transfer function of the servo motor current loop and analyzes the stability of spindle servo motor current loop .

Abstract: For a building under multi-dimensional seismic excitations, a new random vibration analysis based on equivalent excitation method is presented, in which, a new equation of motion of the building is used to depict its dynamics and kinematics features. Since most of the earth shocks are non-stationary random processes, the input power spectral density of the seismic excitations are modulated by a time varying function, and their equivalent excitations are constructed by using continuous wavelet transform, where the continuous wavelet coefficients are calculated by using scales and the evolutionary power spectral density, while the equivalent excitations are constructed by inverse continuous wavelet transform. The random vibration analysis is carried out following the procedures of the equivalent excitation method. A simulation example is given to investigate some affection of the multi-dimensional seismic inputs, especially the rotational one.

Abstract: The dynamic response of Variable Sweep Wing Aircraft (VSWA) with the wing sweeping is presented. The center of gravity (cg) of the aircraft, location of each wing partition , and moment of inertia alter significantly due to the wing morphing, resulting in considerably change of the dynamics of the aircraft. The extended equations of motion (EOMs) suitable for morphing wing aircraft are derived. Compared with the traditional EOMs, there are 4 additional forces and moments exhibiting in the extended EOMs due to the wing morphing. The results show that the additional forces and moments can affect the flight control considerably.

Abstract: This paper investigates the sensorless detection and evaluation of inner oscillations of unknown test objects mounted on a compliant test bench. The principle of the sensorless analysis is that test objects are not totally rigid in reality. This means one or more parts of the test objects are oscillating with different eigenfrequencies compared to their rigid equivalent. By comparing eigenfrequencies of both (rigid and fault test object) oscillating parts are detectable. The aim of this experiment is to demonstrate the use of a 6 DOF compliant Stewart platform (alternatively used in a simulation environment) to generate frequency sweeps in all degrees of freedom, to get a sensorless detection of vibrations in unknown objects. For this purpose only the preexisting sensors applied for the control of the hexapod should be used. The detection of loose parts by shaking objects can be done by a complex robotic manipulation task. Being designed for flexible use by small and medium-sized enterprises, the robotic Stewart platform (hexapod) will adapt autonomously to different test objects leading to a highly flexible robot.

Abstract: A model for a moderately deep underwater explosion bubble was developed in inviscid and irrotational fluid. Considering the effects of gravity, buoyancy, drag to the motion of bubble, the equations of motion (EOM) for bubble in inviscid and irrotational fluid near a free surface were established by introducing the potential-flow theory, energy equation and Hamilton principle. The displacement of the center of bubble, the radius-time histories and impulse periods of bubble were acquired by solving the EOM. The calculated results were compared with the experimental and numerical results. The compared results show that the former is consistent with the latter. The research has value to correlative theory research and engineering calculation.