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On human oscillation characteristics in connection with study of the occupant-vehicle-road system
ABSTRACTS
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psychological information is not available to make such calculation possible) is to base the evaluation of handling on an inverse calculation of the motion, in which case, the transmission function of the driver is not set beforehand, nor is anything predicted. More-over, the apparatus of a steady-state equations can be utilised if vehicle longitudinal speed is constant. The inverse calculation proposed resolves itself into two more simple ones dealing with : (a) the driver transmission function over the guidance input of the system under those conditions where the loading input Fequals 0, and (b) the driver transmission function over the loading input of the system where the guidance input Y equals 0. However, the transmission functions at (a) and (b) cannot be used for compiling the equation of motion of the system and, furthermore, handling of the vehicle is understood as that combination of its qualities determining the level of driver sensori-motor activity necessary for the exact fulfilment of the given law of motion. Two quantitative characteristics of the level of driver sensori-motor activity are possible, viz. numerical values of the phase frequency characteristic of the alteration brought about by the driver in the vehicle-environment-driversystem and numerical values of t he "driver transmission coefficients" necessary for providing stability of the system in motion. The equation presented for transient motion of the vehicle describes small lateral deviations of this from a certain longitudinal axis and, in investigating vehicle response to control, it is assumed that: (1) the transmission function of the system is equal to unity, and (2) the transmission functions of that controlled and that performing the control (the driver) are opposite to one another (inverses). Information on the level of driver sensori-motor activity necessary is presented graphically in the form of the phase frequency characteristic. To assess the interference protection of the system, it is assumed that, despite the action of disturbances on the vehicle, the driver is fully able to compensate for these. Also, in order to establish the driver structure and, hence, describe the control element in analysing the stability of the system in motion, an examination is made of a vehicle-driver system moving in a flat trajectory. (M.I.R.A.) 15.
B. V. Ranganatham and N. Siva Sundara Pandian. Strength and deformation characteristics of anisotropically consolidated Kaolinite clay (in English). Acta Technica 63 (1/4), 253-262 (1968). Consolidation characteristics of natural clay strata differ from those obtained from oedometer and hydrostatic consolidation tests. Hence a modified triaxial testing technique which simulates better the mechanical behavior of a natural deposit is used to obtain strength deformation properties of Kaolinite clay. The results are used to develop expressions for volumetric and axial strains and to study the at rest condition. The extent to which the testing of an isotropically consolidated sample would lead to overestimate the strength of a natural deposit is shown. It depends mainly on the principal stress ratio under which it has been consolidated. (App/. Mech. Rev.)
16.
R. V. Rotenberg and V. N. Sirenko. On human oscillation characteristics in connection with study of the occupant-vehicle-road system. Avtom. Prom. No. 1, 24-26 (January 1972) The authors report investigations forming a sequal to those previously dealt with and in which the following were different from before: (l) the oscillations of parts of the human body during walking and running were regarded as random processes, acceleration traces having shown such oscillations to vary from one step to another in random fashion, (2) accelerations were measured along the three main co-ordinate axes of the human body, since it was noted that, during walking and even more so during running, lateral and longitudinal, beside vertical, oscillations of the trunk and head occur, (3) the mechanical parameters (accelerations) were measured in addition to monitoring physiological values (energy-usage, pulse rate, and lung ventilation, volume), and (4) the oscillations arising during walking and running were compared with those experienced by car occupants. The test subjects were fifteen males between the ages of 18 and 45, and a control group consisting of five of these between the ages of 21 and 24 served to evaluate the stability of the physiological indices with time. Constant disturbance conditions for the test subjects were obtained with a moving tread-band on which it was necessary to walk or run in order to stay in the same place. Accelerations of the head proved to be of a quasi-periodic nature, and, on the basic harmonic describing the raising and lowering of the body as a whole, were found to be superimposed oscillations of the trunk with a natural frequency of 4-0- 6.0 c/see. The customary disturbance frequencies for the individual were within the range 1-2.5 c/sec. Dominant accelerations were those acting vertically; at the low disturbance frequencies, the horizonal and vertical accelerations were approximately the same, but, in the medium-frequency range, the former amounted to only 40 50 per cent of the latter. While the vertical and lateral accelerations of the head were,
70
A BSTRACTS as a rule, smaller than those of the trunk, the situation was reversed with regard to longitudinal accelerations, which then raises the question as to why ride smoothness, developed on the basis of vertical accelerations only, nearly always proves acceptable. Oscillatory motion of the individual is accompanied by a change in his physiological indices. With increase in the disturbance frequency, pulse rate rose slowly, but the energy-usage related to the weight of the individual, etc. grew more quickly. Moreover, the physiological indices were found to depend not only on the disturbance frequency, but also on the time for which the oscillation is present. By the end of a 2-hr test period, both the vertical and horizontal accelerations decreased with slow but increased with rapid walking. The fundamental part of the verticalacceleration spectrum for the head lies within the disturbance-frequency range 0.5-4.0 c/sec. It was also shown that, with growth of walking speed, a component appears in the oscillation spectrum for the trunk which is higher in frequency than the carrier frequency of the walking paces; this frequency (4.5 c/sec) is possibly the natural-oscillation one of the body in the longitudinal direction. In certain cases, the spectral density curves for accelerations during walking and vehicle travel almost coincided. Recommendations are made as to the vertical, longitudinal, and lateral mean-quadratic-acceleration limits for three different conditions of travel. (M.I.R.A.)
17.
E. T. Selig and O. H. Grangaard, Jr. A new technique lor soil strain measurement. Materials Research & Standards 10, (11), 19 21 (November 1970). The device described is handy, rugged, and yet accurate for measurement of static and dynamic strain in soil. The chief features of the system are (i) its easy installation, (ii) facility of operation in most soils at any moisture content, (iii) most important of all, the negligible effect of temperature (the sensors were subjected to a 40°F temperature differential), and (iv) misalignment of sensors through lateral translation and rotation. This last factor is all the more relevant since the sensors are of free floating type. The calibration system apeears to be fairly simple. No mention is made of how the device may work at greater depths within the soil as in measurement of strains within fills or deep excavations. Also the system does not appear too suited for measurement of large movements in soil or rock, as the assumption of electrical signal being a linear function of strain may not be valid. it would be interesting to know what effect still larger diameters of sensors will have (this will mean greater gage length) on the performance of the device. It can be presumed that more details will be forthcoming. The technique can be very usefully put into practice in the accurate measurement of small strains in various fields of soil engineering. (Appl. Mech. Rev.)
18.
V. B. Tsimbalin, V. V. Gnetnev and L. N. Orlov. On the method of analysing accelerations and vehicle ride smoothness. Avtom. Prom. No. 10, 13 (October 1971). The article deals with the analysis of vehicle vertical accelerations and the evaluation of vehicle ride smoothness. It is shown that, in analysing the amplitude/frequency characteristics of the vertical accelerations of, e.g. the centre of the load-carrying platform of a truck (both loaded and empty), a considerable increase in the relative number of accelerations at about 3 c/sec should be expected with the truck empty. Tabulated data on the frequency-distribution of vertical accelerations at the centre of a truck load-carrying platform during operation on a cobbled surface at a speed of 50 km/hr indicate that, without load, the number of accelerations with a mean frequency of 3 c/sec reached 54 per cent, whereas, with load, almost the same percentage of accelerations related to a lower frequency. If the vertical accelerations had been analysed in the frequency range 1 4 c/sec' the difference in the frequency spectrum with and without load would not have been revealed. A similar situation is observed with analysis of the frequency spectrum for the vertical accelerations of the driver's seat ; tabulated data on the frequency distribution of these accelerations show a characteristic change, by a factor of two, in the low-frequency components (1-2 c/sec) in relation to load. It has been noted that, at frequencies of (~8 and 20-25 c/see accelerations are permissible whose magnitude is 2.5-3.0 times smaller than that at frequencies of up to 2 c/sec. Coefficients for correcting evaluations of the influence of oscillations in relation to frequencies observed have been recommended, these coefficients having values of 1.2-11.0, but mostly of the order of 1.7 3-0. The extent of the reduction in vertical acceleration at the centre of a truck load-carrying platform and driver's seat on asphalt and cobbled surfaces with a load instead of the truck being empty is described. In all the cases of truck operation dealt with, the change in vertical-acceleration frequency components must be analysed, together with the change in
69
psychological information is not available to make such calculation possible) is to base the evaluation of handling on an inverse calculation of the motion, in which case, the transmission function of the driver is not set beforehand, nor is anything predicted. More-over, the apparatus of a steady-state equations can be utilised if vehicle longitudinal speed is constant. The inverse calculation proposed resolves itself into two more simple ones dealing with : (a) the driver transmission function over the guidance input of the system under those conditions where the loading input Fequals 0, and (b) the driver transmission function over the loading input of the system where the guidance input Y equals 0. However, the transmission functions at (a) and (b) cannot be used for compiling the equation of motion of the system and, furthermore, handling of the vehicle is understood as that combination of its qualities determining the level of driver sensori-motor activity necessary for the exact fulfilment of the given law of motion. Two quantitative characteristics of the level of driver sensori-motor activity are possible, viz. numerical values of the phase frequency characteristic of the alteration brought about by the driver in the vehicle-environment-driversystem and numerical values of t he "driver transmission coefficients" necessary for providing stability of the system in motion. The equation presented for transient motion of the vehicle describes small lateral deviations of this from a certain longitudinal axis and, in investigating vehicle response to control, it is assumed that: (1) the transmission function of the system is equal to unity, and (2) the transmission functions of that controlled and that performing the control (the driver) are opposite to one another (inverses). Information on the level of driver sensori-motor activity necessary is presented graphically in the form of the phase frequency characteristic. To assess the interference protection of the system, it is assumed that, despite the action of disturbances on the vehicle, the driver is fully able to compensate for these. Also, in order to establish the driver structure and, hence, describe the control element in analysing the stability of the system in motion, an examination is made of a vehicle-driver system moving in a flat trajectory. (M.I.R.A.) 15.
B. V. Ranganatham and N. Siva Sundara Pandian. Strength and deformation characteristics of anisotropically consolidated Kaolinite clay (in English). Acta Technica 63 (1/4), 253-262 (1968). Consolidation characteristics of natural clay strata differ from those obtained from oedometer and hydrostatic consolidation tests. Hence a modified triaxial testing technique which simulates better the mechanical behavior of a natural deposit is used to obtain strength deformation properties of Kaolinite clay. The results are used to develop expressions for volumetric and axial strains and to study the at rest condition. The extent to which the testing of an isotropically consolidated sample would lead to overestimate the strength of a natural deposit is shown. It depends mainly on the principal stress ratio under which it has been consolidated. (App/. Mech. Rev.)
16.
R. V. Rotenberg and V. N. Sirenko. On human oscillation characteristics in connection with study of the occupant-vehicle-road system. Avtom. Prom. No. 1, 24-26 (January 1972) The authors report investigations forming a sequal to those previously dealt with and in which the following were different from before: (l) the oscillations of parts of the human body during walking and running were regarded as random processes, acceleration traces having shown such oscillations to vary from one step to another in random fashion, (2) accelerations were measured along the three main co-ordinate axes of the human body, since it was noted that, during walking and even more so during running, lateral and longitudinal, beside vertical, oscillations of the trunk and head occur, (3) the mechanical parameters (accelerations) were measured in addition to monitoring physiological values (energy-usage, pulse rate, and lung ventilation, volume), and (4) the oscillations arising during walking and running were compared with those experienced by car occupants. The test subjects were fifteen males between the ages of 18 and 45, and a control group consisting of five of these between the ages of 21 and 24 served to evaluate the stability of the physiological indices with time. Constant disturbance conditions for the test subjects were obtained with a moving tread-band on which it was necessary to walk or run in order to stay in the same place. Accelerations of the head proved to be of a quasi-periodic nature, and, on the basic harmonic describing the raising and lowering of the body as a whole, were found to be superimposed oscillations of the trunk with a natural frequency of 4-0- 6.0 c/see. The customary disturbance frequencies for the individual were within the range 1-2.5 c/sec. Dominant accelerations were those acting vertically; at the low disturbance frequencies, the horizonal and vertical accelerations were approximately the same, but, in the medium-frequency range, the former amounted to only 40 50 per cent of the latter. While the vertical and lateral accelerations of the head were,
70
A BSTRACTS as a rule, smaller than those of the trunk, the situation was reversed with regard to longitudinal accelerations, which then raises the question as to why ride smoothness, developed on the basis of vertical accelerations only, nearly always proves acceptable. Oscillatory motion of the individual is accompanied by a change in his physiological indices. With increase in the disturbance frequency, pulse rate rose slowly, but the energy-usage related to the weight of the individual, etc. grew more quickly. Moreover, the physiological indices were found to depend not only on the disturbance frequency, but also on the time for which the oscillation is present. By the end of a 2-hr test period, both the vertical and horizontal accelerations decreased with slow but increased with rapid walking. The fundamental part of the verticalacceleration spectrum for the head lies within the disturbance-frequency range 0.5-4.0 c/sec. It was also shown that, with growth of walking speed, a component appears in the oscillation spectrum for the trunk which is higher in frequency than the carrier frequency of the walking paces; this frequency (4.5 c/sec) is possibly the natural-oscillation one of the body in the longitudinal direction. In certain cases, the spectral density curves for accelerations during walking and vehicle travel almost coincided. Recommendations are made as to the vertical, longitudinal, and lateral mean-quadratic-acceleration limits for three different conditions of travel. (M.I.R.A.)
17.
E. T. Selig and O. H. Grangaard, Jr. A new technique lor soil strain measurement. Materials Research & Standards 10, (11), 19 21 (November 1970). The device described is handy, rugged, and yet accurate for measurement of static and dynamic strain in soil. The chief features of the system are (i) its easy installation, (ii) facility of operation in most soils at any moisture content, (iii) most important of all, the negligible effect of temperature (the sensors were subjected to a 40°F temperature differential), and (iv) misalignment of sensors through lateral translation and rotation. This last factor is all the more relevant since the sensors are of free floating type. The calibration system apeears to be fairly simple. No mention is made of how the device may work at greater depths within the soil as in measurement of strains within fills or deep excavations. Also the system does not appear too suited for measurement of large movements in soil or rock, as the assumption of electrical signal being a linear function of strain may not be valid. it would be interesting to know what effect still larger diameters of sensors will have (this will mean greater gage length) on the performance of the device. It can be presumed that more details will be forthcoming. The technique can be very usefully put into practice in the accurate measurement of small strains in various fields of soil engineering. (Appl. Mech. Rev.)
18.
V. B. Tsimbalin, V. V. Gnetnev and L. N. Orlov. On the method of analysing accelerations and vehicle ride smoothness. Avtom. Prom. No. 10, 13 (October 1971). The article deals with the analysis of vehicle vertical accelerations and the evaluation of vehicle ride smoothness. It is shown that, in analysing the amplitude/frequency characteristics of the vertical accelerations of, e.g. the centre of the load-carrying platform of a truck (both loaded and empty), a considerable increase in the relative number of accelerations at about 3 c/sec should be expected with the truck empty. Tabulated data on the frequency-distribution of vertical accelerations at the centre of a truck load-carrying platform during operation on a cobbled surface at a speed of 50 km/hr indicate that, without load, the number of accelerations with a mean frequency of 3 c/sec reached 54 per cent, whereas, with load, almost the same percentage of accelerations related to a lower frequency. If the vertical accelerations had been analysed in the frequency range 1 4 c/sec' the difference in the frequency spectrum with and without load would not have been revealed. A similar situation is observed with analysis of the frequency spectrum for the vertical accelerations of the driver's seat ; tabulated data on the frequency distribution of these accelerations show a characteristic change, by a factor of two, in the low-frequency components (1-2 c/sec) in relation to load. It has been noted that, at frequencies of (~8 and 20-25 c/see accelerations are permissible whose magnitude is 2.5-3.0 times smaller than that at frequencies of up to 2 c/sec. Coefficients for correcting evaluations of the influence of oscillations in relation to frequencies observed have been recommended, these coefficients having values of 1.2-11.0, but mostly of the order of 1.7 3-0. The extent of the reduction in vertical acceleration at the centre of a truck load-carrying platform and driver's seat on asphalt and cobbled surfaces with a load instead of the truck being empty is described. In all the cases of truck operation dealt with, the change in vertical-acceleration frequency components must be analysed, together with the change in