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In many applications such as structural testing or vehicle collision studies, rotational data are required. Modal analysis will mainly use it to identify rotational Degrees of Freedoms (DOFs) where crash testing will mainly look i...
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In many applications such as structural testing or vehicle collision studies, rotational data are required. Modal analysis will mainly use it to identify rotational Degrees of Freedoms (DOFs) where crash testing will mainly look into rotational inertia. Measuring rotational acceleration can be done by computing measurements from linear sensors but this leads inevitably to an increase in measurement errors. The Kistler quartz rotational accelerometers types 8838 and 8840 have been developed for direct measurement of angular acceleration. In the first part of this paper, we are going to compare the internal design of the rotation accelerometers type 8838 and 8840 to solutions based on computing measurements from linear sensors. We will look into optimization of the assembly as well as a calibration procedure. In the second part of this paper we will focus on how the rotational sensors have been used to identify and investigate shaker planar rotation. We will then look into how these undesirable planar rotations can influence linear sensor measurement.
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When a falling rock block strikes the ground, the block does not bounce much. This energy loss can be simply represented by the coefficient of restitution for mass point motion. In this paper, dependence of the tangential componen...
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When a falling rock block strikes the ground, the block does not bounce much. This energy loss can be simply represented by the coefficient of restitution for mass point motion. In this paper, dependence of the tangential component of the coefficient of restitution on the incoming angle and the surface friction angle is examined under the normal component being kept constant. A small scale laboratory test is reported to get a better understanding during/at impact. Under the condition in which the normal component has set to be (roughly) constant, it has been recognized that the tangential component of the coefficient restitution R_(et) is a roughly constant when the incoming angle is small and then increases with the increase in the slope angle. This nature of impact is explained by 'sticking' behavior and the transition to slippage. In the transition zone, the ratio of E_r/E_v (rotational/translational energy) has been decreased, however, we cannot conclude that this transition behavior result in the apparent friction reduction with the momentum or sticking with some slippage during the contact.
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As humanoid robotics advances beyond bipedal walking, complex motions involving the whole body are necessary. Most recent humanoids represent the range of motion of the human spine with a single rotation joint. While this joint al...
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As humanoid robotics advances beyond bipedal walking, complex motions involving the whole body are necessary. Most recent humanoids represent the range of motion of the human spine with a single rotation joint. While this joint allows the body to swing during dynamic walking, any bending must be performed only with the legs. This paper develops a skewed rotation plane (SRP) waist joint to give a humanoid robot the same range of torso motion as a human. The SRP design reduces holding torque compared to a orthogonal-axis joint. An inverse kinematics solver using Jacobian Pseudo-inverse was developed to produce smooth torso orientation trajectories. Finally, a mechanical prototype developed and fitted to Drexel University's Jaemi Hubo to verify and validate the model.
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In many coating chambers substrates are moved by simple or planetary rotary motion systems. Isaac Newton already taught that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force. To...
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In many coating chambers substrates are moved by simple or planetary rotary motion systems. Isaac Newton already taught that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force. To move a substrate on a rotary trajectory, centripetal and gravitational forces must act upon the substrate. The substrate must be somehow confined. Confinement options range from firm attachment to a fixture to loose placement in a pocket. Depending on the rotary motion pattern, a loosely held substrate may slide once against a confinement boundary and then stay, or may constantly slide around. 'Rattling around' may be undesirable as it could lead to edge destruction, debris formation, precession of the substrate, and other adverse effects. Firm attachment is advantageous in most cases, but often adds process complexity. We examine the forces present on substrates in typical rotary motion systems and discuss the implications of different confinement methods.
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摘要 :
In many coating chambers substrates are moved by simple or planetary rotary motion systems. Isaac Newton already taught that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force. To...
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In many coating chambers substrates are moved by simple or planetary rotary motion systems. Isaac Newton already taught that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force. To move a substrate on a rotary trajectory, centripetal and gravitational forces must act upon the substrate. The substrate must be somehow confined. Confinement options range from firm attachment to a fixture to loose placement in a pocket. Depending on the rotary motion pattern, a loosely held substrate may slide once against a confinement boundary and then stay, or may constantly slide around. 'Rattling around' may be undesirable as it could lead to edge destruction, debris formation, precession of the substrate, and other adverse effects. Firm attachment is advantageous in most cases, but often adds process complexity. We examine the forces present on substrates in typical rotary motion systems and discuss the implications of different confinement methods.
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Rotational seismology is a relatively new area of science,which was formed in the past 20 years.During this time,new instruments were created;interesting data was obtained and verified;and main directions for further development o...
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Rotational seismology is a relatively new area of science,which was formed in the past 20 years.During this time,new instruments were created;interesting data was obtained and verified;and main directions for further development of rotational seismology were identified.Now a much greater number of observations are required for further development of rotational seismology.We need to create networks for recording of rotational movements,which should be taken parallel to the traditional seismometrical measurements.This requires development of appropriate metrological standards.It is necessary in order for the seismological data to be useful.More detailed views on this issue are presented in this work.
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An external motorize system with an active-caster is presented in this paper. The external motorize system is for driving a manual (hand propelled) wheelchair by electric power by mounting the external device with electric motors,...
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An external motorize system with an active-caster is presented in this paper. The external motorize system is for driving a manual (hand propelled) wheelchair by electric power by mounting the external device with electric motors, a set of batteries, a joystick and motor controllers on a manual wheelchair. In spite of a single drive wheel, 2DOF of the wheelchair with an active-caster drive system can be controlled independently without any constraint, such as the orientation of the drive wheel which is well known as a non-holonomic constraint. A kinematic model of the wheelchair and that with an active-caster drive system are analyzed and a control method for propelling the wheelchair by using a 2DOF joystick is derived. Based on the kinematic model, a prototype mechanism of the active-caster is designed and mounted on a manual wheelchair to realize the motorized manual wheelchair. In the experiments, the independent 2DOF motion can be achieved by the control of the active-caster in which the wheelchair shows successful translation and rotation motions which includes flip motion of the active-caster mechanism.
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To analyze the characteristics of ocean surface backscatter signals, the first-order high frequency (HF) radar ocean surface cross section is mathematically developed for the case of an omnidirectional transmitting/receiving anten...
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To analyze the characteristics of ocean surface backscatter signals, the first-order high frequency (HF) radar ocean surface cross section is mathematically developed for the case of an omnidirectional transmitting/receiving antenna being installed on the shipborne platform with rotation motion. The developed cross section could be degenerated to a stationary monostatic land-based case. The simulations are carried out under different radar parameters and sea states. The results show that the rotation motion has an important influence on radar Doppler spectrum, which may bring significant implications in future investigations for detection of sea targets and ocean remote sensing.
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Motion control of rotational moulding is an area which has not been extensively investigated beyond the current trial and error approach. Different motion control schemes will lead to varied powder flow regimes which exhibit diffe...
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Motion control of rotational moulding is an area which has not been extensively investigated beyond the current trial and error approach. Different motion control schemes will lead to varied powder flow regimes which exhibit different levels of mixing and temperature uniformity. Rotational moulding is hampered by long cycle times. Choosing the ideal rotational speed should allow the optimum use of the inputted heat energy to cause all of the powder bed to become 'tacky' and adhere to the mould wall in the shortest time period. This paper investigates the hypothesis that the optimum rotational speed should be chosen by considering the flow regime of the powder bed at the bottom of the mould, in order to reduce manufacturing time and energy consumption. Experiments were completed to validate this approach using a cylindrical mould under uni-axial rotation. Results show that the ideal rotational speed is found when the powder is flowing in a rolling regime and suggests that further cycle time savings could be achieved by varying the speed during the heating cycle. The effect of rotational speed on part quality (wall thickness uniformity) was also investigated.
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The problem of stabilization of the image sequence from a camera mounted on a moving platform such as airborne reconnaissance is considerably more complex. Motion composed of not only translation but also rotation is a very common...
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The problem of stabilization of the image sequence from a camera mounted on a moving platform such as airborne reconnaissance is considerably more complex. Motion composed of not only translation but also rotation is a very common. For the long focus, long-range imaging system, to estimate and compensate rotation movement between the frames is very important. Through analyzing the effect of rotation on the quality of video sequence, the paper proposes an effective algorithm applied to the rotation and translation movement estimation. This algorithm is composed of three parts: Firstly, the image is divided to many regions and make sure that every pixel motion in each region is uniform; Secondly, the translations vector of each region are obtained by representative point matching technique. Finally the globe motion vectors (include translation and rotation) between the reference frame and the current frames is obtained by solution of a set of linear equations which come form a given affine motion model. Compensation method of motion among the frames is also an important factor to affect the stability of image sequence. If the image sequence is compensated directly with the acquired movement vectors, it will feel the jumping among frames. In the paper, the parameters to compensate for the current image have be determined by average value filtering and been applied to given motion model to stabilize the image stream. It can realize smoothly processing to assure the image sequences stabilization.
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