We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuratio...We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuration lessens wear, increases load capacity, and improves efficiency. The threaded chain consists of nut-shaped links. This paper presents the results of tests carried out on a prototype with a reduction ratio of 46.展开更多
A cycloidal speed reducer employing gears with permanent magnets acting as teeth is described. The magnets, which have their axes radially oriented in both the orbiting gear and the fixed internal gear, are inserted i...A cycloidal speed reducer employing gears with permanent magnets acting as teeth is described. The magnets, which have their axes radially oriented in both the orbiting gear and the fixed internal gear, are inserted in holes drilled in nonmagnetic rims without protruding from the cylindrical exposed surfaces. Because the orbiting gear is not restrained radially, it contacts the fixed gear and rolls on its inner surface. A normal force is developed at the contact point between the gears to balance the magnetic attraction and the centrifugal force of the orbiting gear. The friction available due to this normal force increases the transmission’s torque capacity, which is further increased by elimination of the gap between the gears. Also, the radial load on the supporting orbiting gear bearing is eliminated. A prototype with a reduction ratio of 26 is being tested.展开更多
This brief proposes an area and speed efficient implementation of symmetric finite impulse response (FIR) digital filter using reduced parallel look-up table (LUT) distributed arithmetic (DA) based approach. The compl...This brief proposes an area and speed efficient implementation of symmetric finite impulse response (FIR) digital filter using reduced parallel look-up table (LUT) distributed arithmetic (DA) based approach. The complexity lying in the realization of FIR filter is dominated by the multiplier structure. This complexity grows further with filter order, which results in increased area, power, and reduced speed of operation. The speed of operation is improved over multiply-accumulate approach using multiplier less conventional DA based design and decomposed DA based design. Both the structure requires B clock cycles to get the filter output for the input width of B, which limits the speed of DA structure. This limitation is addressed using parallel LUTs, called high speed DA FIR, at the expense of additional hardware cost. With large number of taps, the number of LUTs and its size also becomes large. In the proposed method, by exploiting coefficient symmetry property, the number of LUTs in the decomposed DA form is reduced by a factor of about 2. This proposed approach is applied in high speed DA based FIR design, to obtain area and speed efficient structure. The proposed design offers around 40% less area and 53.98% less slice-delay product (SDP) than the high throughput DA based structure when it’s implemented over Xilinx Virtex-5 FPGA device-XC5VSX95T-1FF1136 for 16-tap symmetric FIR filter. The proposed design on the same FPGA device, supports up to 607 MHz input sampling frequency, and offers 60.5% more speed and 67.71% less SDP than the systolic DA based design.展开更多
Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and r...Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and reduced speed limit signs—on driver speeding behavior using a medium-fidelity driving simulator. The speed photo enforced and reduced speed limit signs were placed at intervals before the start of the work zone and in the work zone. A virtual work zone network was built to replicate the Baltimore–Washington Parkway(MD-295). A total of 66 participants from different socioeconomic backgrounds participated in 264 driving simulation sessions. The speeds were measured over four phases: initial speed area, sign visible area, sign readable area and post sign area. An analysis of variance and post hoc analysis showed that the speed photo enforced sign was the most effective of the three signs. The second speed photo enforced sign within the work zone was more effective at reducing speed than the sign before the start of the work zone, especially in the post sign area. It was observed that female participants tend to slow down more when encountering a speed photo enforcement sign.展开更多
A visible magnified and simulated nozzle was designed and installed on a winding machine according to the similarity principle of Reynolds number,to study the yarn motion track in hairiness-reducing nozzle.High-speed ...A visible magnified and simulated nozzle was designed and installed on a winding machine according to the similarity principle of Reynolds number,to study the yarn motion track in hairiness-reducing nozzle.High-speed photography was used to observe the yarn instantaneous motion state in the nozzle.The results show that the yarn motion track seems to be a cylindrical helix which is close to inner wall in the twisting chamber and kept the same with different technical parameters,such as diameter of the twisting chamber and jet pressure in orifices.According to simulation results and reasonable simplification,the motion track equation and the rotational equation of the yarn could be derived.The velocity of the swirl and hairiness is faster than that of the yarn balloon,so there is enough time for hairiness to be wrapped into the main body of yarn and hence the hairiness is reduced.展开更多
文摘We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuration lessens wear, increases load capacity, and improves efficiency. The threaded chain consists of nut-shaped links. This paper presents the results of tests carried out on a prototype with a reduction ratio of 46.
文摘A cycloidal speed reducer employing gears with permanent magnets acting as teeth is described. The magnets, which have their axes radially oriented in both the orbiting gear and the fixed internal gear, are inserted in holes drilled in nonmagnetic rims without protruding from the cylindrical exposed surfaces. Because the orbiting gear is not restrained radially, it contacts the fixed gear and rolls on its inner surface. A normal force is developed at the contact point between the gears to balance the magnetic attraction and the centrifugal force of the orbiting gear. The friction available due to this normal force increases the transmission’s torque capacity, which is further increased by elimination of the gap between the gears. Also, the radial load on the supporting orbiting gear bearing is eliminated. A prototype with a reduction ratio of 26 is being tested.
文摘This brief proposes an area and speed efficient implementation of symmetric finite impulse response (FIR) digital filter using reduced parallel look-up table (LUT) distributed arithmetic (DA) based approach. The complexity lying in the realization of FIR filter is dominated by the multiplier structure. This complexity grows further with filter order, which results in increased area, power, and reduced speed of operation. The speed of operation is improved over multiply-accumulate approach using multiplier less conventional DA based design and decomposed DA based design. Both the structure requires B clock cycles to get the filter output for the input width of B, which limits the speed of DA structure. This limitation is addressed using parallel LUTs, called high speed DA FIR, at the expense of additional hardware cost. With large number of taps, the number of LUTs and its size also becomes large. In the proposed method, by exploiting coefficient symmetry property, the number of LUTs in the decomposed DA form is reduced by a factor of about 2. This proposed approach is applied in high speed DA based FIR design, to obtain area and speed efficient structure. The proposed design offers around 40% less area and 53.98% less slice-delay product (SDP) than the high throughput DA based structure when it’s implemented over Xilinx Virtex-5 FPGA device-XC5VSX95T-1FF1136 for 16-tap symmetric FIR filter. The proposed design on the same FPGA device, supports up to 607 MHz input sampling frequency, and offers 60.5% more speed and 67.71% less SDP than the systolic DA based design.
基金the Maryland State Highway Association (SHA) for its funding support throughout the study
文摘Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and reduced speed limit signs—on driver speeding behavior using a medium-fidelity driving simulator. The speed photo enforced and reduced speed limit signs were placed at intervals before the start of the work zone and in the work zone. A virtual work zone network was built to replicate the Baltimore–Washington Parkway(MD-295). A total of 66 participants from different socioeconomic backgrounds participated in 264 driving simulation sessions. The speeds were measured over four phases: initial speed area, sign visible area, sign readable area and post sign area. An analysis of variance and post hoc analysis showed that the speed photo enforced sign was the most effective of the three signs. The second speed photo enforced sign within the work zone was more effective at reducing speed than the sign before the start of the work zone, especially in the post sign area. It was observed that female participants tend to slow down more when encountering a speed photo enforcement sign.
基金Tianjin Science and Technology Planning Projects,China(No.04310471)
文摘A visible magnified and simulated nozzle was designed and installed on a winding machine according to the similarity principle of Reynolds number,to study the yarn motion track in hairiness-reducing nozzle.High-speed photography was used to observe the yarn instantaneous motion state in the nozzle.The results show that the yarn motion track seems to be a cylindrical helix which is close to inner wall in the twisting chamber and kept the same with different technical parameters,such as diameter of the twisting chamber and jet pressure in orifices.According to simulation results and reasonable simplification,the motion track equation and the rotational equation of the yarn could be derived.The velocity of the swirl and hairiness is faster than that of the yarn balloon,so there is enough time for hairiness to be wrapped into the main body of yarn and hence the hairiness is reduced.
