This paper proposes an incipient slip detection method for a robotic hand based on the vibration power of the pressure center. Firstly,an array-type pressure sensor was planted into the soft skin of the robotic hand t...This paper proposes an incipient slip detection method for a robotic hand based on the vibration power of the pressure center. Firstly,an array-type pressure sensor was planted into the soft skin of the robotic hand to measure the stick-slip vibration component of the pressure center generated in the process of slip of the grasped object. Secondly,the vibration power of the pressure center was calculated based on the measured stick-slip vibration component,and was used as a slip-detection function to judge the incipient slip of the grasped object. Finally,in order to use the same threshold value to judge incipient slip for different grasping forces,a weight coefficient was experimentally identified and used in the slip-detection function. The effectiveness of the proposed slip detection method was verified by experimental results,which showed that incipient slip can be detected by the proposed slip-detection function with the same threshold value for various materials,different slipping speeds grasping forces. In addition,multiple iterations of the experiment had demonstrated that the slip detection is repeatable.展开更多
This study aimed to examine the effects of open/ closed eyes and age difference on Center of Foot Pressure (COP) sway during stepping. The subjects were 87 healthy males aged 10 - 80 years. COP was measured 20 times w...This study aimed to examine the effects of open/ closed eyes and age difference on Center of Foot Pressure (COP) sway during stepping. The subjects were 87 healthy males aged 10 - 80 years. COP was measured 20 times when subjects stepped on two force plates (left and right) at a rate of 60 steps/min. The evaluation parameters selected were: total trace length, velocity, circumference, rectangular area,left-right width, and front-back width. The former four of these parameters were found to be significantly lower with eyes open than eyes closed in 80-year-old subjects, while the last parameter was significantly lower with eyes open in 10-year-old subjects. In 70- and 80-year-old subjects with eyes open, circumference was greater than that in 10- and 40 - 60-year-old subjects;their rectangular area was greater than that in 50- and 60-year-old subjects;and, their front-back width was greater than that in 10- and 30 - 60-year-old subjects. With eyes closed, circumference, rectangular area, left-right width, and front-back width in 80-year- old subjects, were greater than those in 10 - 70- year-old subjects. The front-back width during stepping with eyes closed was greater in 70- and 80-year-old subjects than in 30 - 50-year-old subjects. The Romberg quotient for all COP sway parameters revealed no significant age-related differences. From our findings, a difference in body sway was observed in 80-year-old subjects (with eyes open/closed) when compared with the other age groups. In addition, the extent of sway varied little among 80 year-old- subjects have greater body sway during stepping, particularly with eyes closed.展开更多
In order to improve lubricating characteristics of slippers in an axial piston pump, the combining center cavity slipper approach was proposed based on slipper shape and moving characteristic. The cylindrical coordina...In order to improve lubricating characteristics of slippers in an axial piston pump, the combining center cavity slipper approach was proposed based on slipper shape and moving characteristic. The cylindrical coordinate was used in the lubricant area and mesh was made. The blockweight approach was implemented to deal with non-coincidence of mesh and shallow recess border in numerical method. The finite control volume method was applied in calculating pressure distribution. The flow conservation equation and film thickness model were resolved through Gauss-Siedel relaxation iteration. The calculation and analysis results indicate that compared to the slipper （1） slip- per pressure distribution is improved; （2） hydrodynamic pressure of the combining slipper is greatly increased; （3） inclining degree is greatly reduced; （4） negative pressure in lubricant film disappear. So the combining center cavity slipper is lubricated better.展开更多
Aiming at harsh environment of cluster bombs center tube explosion dispersion and difficulties in installation of traditional test systems,a storage test system based on 16-bit ultra-low power microcontroller MSP430 i...Aiming at harsh environment of cluster bombs center tube explosion dispersion and difficulties in installation of traditional test systems,a storage test system based on 16-bit ultra-low power microcontroller MSP430 is designed in order to acquire gas pressure during cluster bombs dispersion.To meet the requirement of low power consumption,the working states of system＇s modules during data acquisition are elaborated and the equation to calculate the gas pressure change during cylindrical center tube opening the hatch is deduced.The field test is conducted and good test results are obtained.展开更多
Background:Combined knee valgus and tibial internal rotation(VL+IR)moments have been shown to stress the anterior cruciate ligament(ACL)in several in vitro cadaveric studies.To utilize this knowledge for non-contact A...Background:Combined knee valgus and tibial internal rotation(VL+IR)moments have been shown to stress the anterior cruciate ligament(ACL)in several in vitro cadaveric studies.To utilize this knowledge for non-contact ACL injury prevention in sports,it is necessary to elucidate how the ground reaction force(GRF)acting point(center of pressure(CoP))in the stance foot produces combined knee VL+IR moments in risky maneuvers,such as cuttings.However,the effects of the GRF acting point on the development of the combined knee VL+IR moment in cutting are still unknown.Methods:We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector’s directional probability for developing the combined knee VL+IR moment,and theoretically predicted that when the CoP is posterior to the tibial rotational axis,the GRF vector is more likely to produce the combined knee VL+IR moment than when the CoP is anterior to the tibial rotational axis.Then,we tested a stochastic aspect of our theory in a lab-controlled in vivo experiment.Fourteen females performed 60˚cutting under forefoot/rearfoot strike conditions(10 trials each).The positions of lower limb markers and GRF data were measured,and the knee moment due to GRF vector was calculated.The trials were divided into anterior-and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike,and the occurrence rate of the combined knee VL+IR moment was compared between trial groups.Results:The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL+IR moment(maximum of 82.8%)at every time point than those of the anterior-CoP trials,as theoretically predicted by the deterministic mechanical condition.Conclusion:The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL+IR stress.展开更多
文摘This paper proposes an incipient slip detection method for a robotic hand based on the vibration power of the pressure center. Firstly,an array-type pressure sensor was planted into the soft skin of the robotic hand to measure the stick-slip vibration component of the pressure center generated in the process of slip of the grasped object. Secondly,the vibration power of the pressure center was calculated based on the measured stick-slip vibration component,and was used as a slip-detection function to judge the incipient slip of the grasped object. Finally,in order to use the same threshold value to judge incipient slip for different grasping forces,a weight coefficient was experimentally identified and used in the slip-detection function. The effectiveness of the proposed slip detection method was verified by experimental results,which showed that incipient slip can be detected by the proposed slip-detection function with the same threshold value for various materials,different slipping speeds grasping forces. In addition,multiple iterations of the experiment had demonstrated that the slip detection is repeatable.
文摘This study aimed to examine the effects of open/ closed eyes and age difference on Center of Foot Pressure (COP) sway during stepping. The subjects were 87 healthy males aged 10 - 80 years. COP was measured 20 times when subjects stepped on two force plates (left and right) at a rate of 60 steps/min. The evaluation parameters selected were: total trace length, velocity, circumference, rectangular area,left-right width, and front-back width. The former four of these parameters were found to be significantly lower with eyes open than eyes closed in 80-year-old subjects, while the last parameter was significantly lower with eyes open in 10-year-old subjects. In 70- and 80-year-old subjects with eyes open, circumference was greater than that in 10- and 40 - 60-year-old subjects;their rectangular area was greater than that in 50- and 60-year-old subjects;and, their front-back width was greater than that in 10- and 30 - 60-year-old subjects. With eyes closed, circumference, rectangular area, left-right width, and front-back width in 80-year- old subjects, were greater than those in 10 - 70- year-old subjects. The front-back width during stepping with eyes closed was greater in 70- and 80-year-old subjects than in 30 - 50-year-old subjects. The Romberg quotient for all COP sway parameters revealed no significant age-related differences. From our findings, a difference in body sway was observed in 80-year-old subjects (with eyes open/closed) when compared with the other age groups. In addition, the extent of sway varied little among 80 year-old- subjects have greater body sway during stepping, particularly with eyes closed.
基金Supported by the National Key Laboratory Foundation Project(9140C3403010903)
文摘In order to improve lubricating characteristics of slippers in an axial piston pump, the combining center cavity slipper approach was proposed based on slipper shape and moving characteristic. The cylindrical coordinate was used in the lubricant area and mesh was made. The blockweight approach was implemented to deal with non-coincidence of mesh and shallow recess border in numerical method. The finite control volume method was applied in calculating pressure distribution. The flow conservation equation and film thickness model were resolved through Gauss-Siedel relaxation iteration. The calculation and analysis results indicate that compared to the slipper （1） slip- per pressure distribution is improved; （2） hydrodynamic pressure of the combining slipper is greatly increased; （3） inclining degree is greatly reduced; （4） negative pressure in lubricant film disappear. So the combining center cavity slipper is lubricated better.
文摘Aiming at harsh environment of cluster bombs center tube explosion dispersion and difficulties in installation of traditional test systems,a storage test system based on 16-bit ultra-low power microcontroller MSP430 is designed in order to acquire gas pressure during cluster bombs dispersion.To meet the requirement of low power consumption,the working states of system＇s modules during data acquisition are elaborated and the equation to calculate the gas pressure change during cylindrical center tube opening the hatch is deduced.The field test is conducted and good test results are obtained.
基金supported by the Grant-in-Aid for Young Scientists(B)Project(Grant No.24700716)funded by the Ministry of Education,Culture,Sports,Science and Technology,Japan.
文摘Background:Combined knee valgus and tibial internal rotation(VL+IR)moments have been shown to stress the anterior cruciate ligament(ACL)in several in vitro cadaveric studies.To utilize this knowledge for non-contact ACL injury prevention in sports,it is necessary to elucidate how the ground reaction force(GRF)acting point(center of pressure(CoP))in the stance foot produces combined knee VL+IR moments in risky maneuvers,such as cuttings.However,the effects of the GRF acting point on the development of the combined knee VL+IR moment in cutting are still unknown.Methods:We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector’s directional probability for developing the combined knee VL+IR moment,and theoretically predicted that when the CoP is posterior to the tibial rotational axis,the GRF vector is more likely to produce the combined knee VL+IR moment than when the CoP is anterior to the tibial rotational axis.Then,we tested a stochastic aspect of our theory in a lab-controlled in vivo experiment.Fourteen females performed 60˚cutting under forefoot/rearfoot strike conditions(10 trials each).The positions of lower limb markers and GRF data were measured,and the knee moment due to GRF vector was calculated.The trials were divided into anterior-and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike,and the occurrence rate of the combined knee VL+IR moment was compared between trial groups.Results:The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL+IR moment(maximum of 82.8%)at every time point than those of the anterior-CoP trials,as theoretically predicted by the deterministic mechanical condition.Conclusion:The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL+IR stress.
