The purpose of this study was to elucidate the muscular influence of microvibration (MV) and to apply MV to the evaluation of a medical index for dystrophy patients. Subjects were 10 myotonic dystrophy patients (MD; 7 males and 3 females, 43.5±8.2 years), five limb-girdle patients in progressive muscular dystrophy (LG; 4 males and 1 female, 38.6±12.7 years), and 12 normal subjects (males, 21.0±2.0 years) being treated for comparison. Muscular function data for the patients (function stage, grip strength, and pinching force) were measured before the experiment. Metric data (length and girth of upper limb) were also measured. Subjects sat on chairs and laid their right forearm on an elbow rest. MV's at eyelid, m. biceps brachii, and right thenar were detected by MT-3 T. Physiological tremor at the palm was measured by a miniature accelerator. The order used in the experiment was resting state for two minutes, maximum voluntary contraction (MVC), the holding of 60% MVC for one minute, and resting state for three minutes. The MV and physiological tremor data for each one minute were analyzed by (a) integrated amplitude of five bands in the range from 2 to 30Hz, and (b) the first peak frequency of power spectrum. The evaluations of the amplitude and peak frequency and the data of the muscular functions and metrics were all studied by principal component analysis in order to find correlations among the data. MV for eyelid, m. biceps brachii, and thenar showed the characteristic main bands, i. e., delta band (2-4Hz), alpha band (8-13Hz), and theta band (4-8Hz), respectively. MV amplitude for the patients was lower than that, for normal subjects. MV amplitude for the normal subjects increased during 60% MVC, but this phenomenon was not recognized in the patients. Similar results were shown in the first peak frequency: The peak frequency for the patients waslower by 2 Hz than that for the normal controls and was hardly influenced by conditions like rest or load. Differences in peak frequency and amplitude between MD patients and normal controls were at a level of 1% significance. The results of principal component analysis denoted that the function stage closely correlated to the peak frequency of MV at thenar and m. biceps brachii and to the metrics of the upper limb. The above results showed that MV was affected by muscles. Therefore, the influence of the neuromuscular system (i. e., gamma motor system) would seem to be related to the mechanism of MV. Moreover, as the medical index of MV, peak frequency and amplitude for MD and LG were lower than that for the normal subjects. This tendency was emphasized by imposing increased load.

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A new model of physiological tremor has been developed in order to establish an analytical procedure for extracting physiological information from the data of tremor frequencies. The model is basically an equation of motion composed of the second-order mechanical system and the spinal and supraspinal reflex loops. The following two parameters are introduced in the model: 1) the gain ratio of the two reflex loops (long-loop gain/short-loop gain), and 2) a characteristic frequency inversely proportional to the difference of the two delay times, which corresponds to a fixed point in the graph of the reflex term of the phase angle equation. The sustained oscillation frequencies are theoretically determined from the intersections of the curves of the mechanical and reflex terms of the phase angle equation. If the gain ratio is less than unity, there are generally three intersections. It is predicted that the two lower frequencies may possibly be observed as a doublet line spectrum (frequency splitting) if they are close to each other. In order to validate the model, sustained oscillations of the hand with an added weight were measured during slow relaxing movement. Damped oscillations after a tap were also measured. The advantages of the slow relaxing movement for tremor generation are relatively large amplitude and sinusoidal wave form of the oscillations. Mechanical oscillations were selected from the damped oscillations using a criterion of half-power band width to calculate the mechanical parameters. As the model predicted, a doublet line spectrum of the sustained oscillation was observed under a specific loading condition, supporting the model and enabling us to calculate the reflex parameters. The best fitting reflex parameters including the delay times and the gain ratio of the two reflex loops were obtained using a least-square criterion. The long-and short-loop delay times are estimated to be 71ms and 25ms, respectively, and the loop-gain ratio is less than unity. The behavior of the tremor frequency was simulated as a function of the loop-gain ratio using the parameters of the hand described above. The results of the simulation reveal that the doublet line spectrum occurs in a certain range of the gain ratio when it is less than unity, and as it increases further, the frequency decreases asymptotically to a certain limit. Based on the model the variability in tremor frequency in various experimental situations can be explained satisfactorily as a change in the loop-gain ratio.

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For image sensing, the solid-state image sensor is now the most popular device. However, such devices, including the videcon tube, merely transfer the optical image into an electrical signal with corresponding intensity and color profiles of the image without processing or discriminating signals for higher level uses, such as pattern recognition or robot eyes. In addition, the sensitivity and the aperture size must be adjusted according to the external optical environment. In the vertebrate retina, on the other hand, the receptor can adapt its sensitivity automatically to an appropriate level. In the outer plexiform layer, receptors (rods and cones), horizontal cells, and bipolar cells make complex circuits including feedback mechanisms and center/surround organizations. These circuits and their functionings are studied widely in physiology and morphology by utilizing glass micro-electrode and intracellular dying techniques. The basic features of the outer plexiform layer are in (band-pass type) spatial filtering, which improves the contrast sensitivity, and in color-coding mechanisms. This paper discusses spatial characteristics and the opponent color mechanisms in this layer. Spatial characteristics: Three types of cone with a peak action spectrum at blue, green, and red were electrically connected by type, producing a spatial summation within 100 to 200μm ranges. Enlarging the spot diameter caused increasing response amplitude within this range. However, further enlargement did not produce a more enlarged response, but a decrease due to the feedback signal from the horizontal cells. The horizontal cell exhibited tremendously wide spatial summation over a few mm due to the electrical coupling through the gap junctions. A two-dimensional discrete horizontal cell network model was proposed and analyzed. The model interpreted the experimental data with good results. Receptor and horizontal cell signals input to the bipolar cell with an opposite sign and thus form the center/surround organization at this stage. This was confirmed by matching the subtraction of the two experimental data (R and H) with the bipolar cell area effect characteristics. Opponent color mechanism: The three primary color signals were converted to the opponent color signals through the feedback path (H to cones) in the outer plexiform layer, that is, R/G/B to R+G-and Y+B-, in the carp retina horizontal cell. According to the center/surround organization described above and these chromatic type horizontal cells with the ON and OFF bipolar channels, all the opponent color signals are established at this level. Four types of opponent color receptive fields are found in the carp retina: center opponent, surround opponent, spatially segregated opponent, and double opponent. The possible wiring diagrams for each type are presented.

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The vibration problems related to living bodies have so far been studied from the perspectives of engineering, physiology, and psychology. This study shows the relationship between vibratory sensibility and temperature in the living body. Psychological experiments were carried out by using the vibrometer of an acoustical calibration apparatus in sine, triangular and square waves. The sensibility-threshold measurements were made using 30-700 Hz sine waves, 30-300Hz triangular and sawtooth waves, or 30-250Hz square waves. Each of ten subjects was kept seated. The average value of the vibratory levels, varied by ascending and descending steps, was taken as that of the threshold. As the vibrometer in the apparatus used makes a noise at frequencies greater than 250 Hz, it was masked from the subject by presenting him with a different noise. The threshold curve for square waves was lower by 12.3 dB than that for sine waves at about 30Hz. The threshold curve of the 26℃ sine wave was lower by 10 dB than that of the 58℃ sine wave vibration near 200 Hz. At frequency stimulation higher than 120 Hz, as the temperature of the contact point was lowered, the amplitude threshold increased and the frequency at which the threshold curve was at a minimum shifted to a lower frequency. In addition, a model of the vibratory sensibility system was constructed by electronic circuits. Its spatio-temporal characteristics were compared with the neurophysiological and psychological data on human vibratory sensibility. The results showed qualitative agreement with the fundamental neurophysiological and psychological data.

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Pain sensations on the skin are generated by mechanical nociceptive stimuli. However, the question of what constitutes a mechanical nociceptive stimulus is still unclear. Therefore, in this study, mechanical factors which cause cutaneous mechanical nociception were investigated by computer simulation of an elastic model of the skin. In order to compare them with the results of the simulation, psycho-physical experiments on awake human subjects were performed. Indentation threshold which is indentation amplitude of the stimulus needle from the skin surface to the depth where the pin prick is first felt, were measured as a parameter of stimulus for various pins and cylindrical needles. The apparatus which measured indentation thresholds was composed of a touch sensor which detects the initial touch of the needle to the skin, a noncontacting type displacement measurement device which measures the amplitude of displacement of the needle, and the button by which the subject indicates the threshold of pain sensation. The results showed that sharp pins had shallower indentation thresholds and cylinders with small radii had shallower thresholds. The elastic model of the skin was based on the three-dimensional elastic theory that assumes that the skin is a homogeneous, isotropic, and semiinfinite elastic medium. The nociceptors, the receptors of pain sensation, were supposed to be distributed pseudo randomly at a certain depth in the skin. Each nociceptor was assumed to respond to a mechanical factor such as vertical strain, horizontal stress, and so on. The indentation threshold was defined as the smallest indentation amplitude of the needle on which the mechanical factor at one of nociceptors reached the predetermined threshold. The value of the threshold was determined to give a fit between the result of simulation and experimental observation for one of the needles. Setting the threshold at this value, indentation thresholds of other needles were examined by computer simulation, and a comparison with the experimental results was made. In all, twenty kinds of mechanical factors, stresses, strains, principal stresses and strains, and differentials of strains were included in the hypothesis for adequate stimulus to the nociceptor. Computer simulation showed that the vertical differential of vertical compressive strain and the vertical differential of averaged horizontal tensile strain explained the experiment most effectively. From this result these two differentials of strain are considered to be the candidates for the mechanical factor of nociception.

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The articular cartilage has a remarkable ability, to soften and spread loads evenly onto the subchondral bone. Smooth joint movement with low friction can be performed, thanks to this "elasto hydrodynamic lubrication". We have examined the mechanical properties of the articular cartilage of rat and rabbit tibia using an experimental apparatus with which the indentation deformation of the cartilage can be measured through micro-transducer. Time-dependent deformation of the articular cortilage under constant loading or repeated loading can be measured with this apparatus. The articular cartilage showed instantaneous deformation just after the application of the load, gradual time-dependent deformation, which is called "creep deformation", and instantaneous recovery of deformation after removal of the load, followed by gradual recovery. Such deformation was, however, not observed, when the indentation test was performed in air rather than in saline. When the indentation test was performed, in silicone oil, morphological changes of the articular surface could be observed microscopically. We could observe the exudation of fluid from the articular cartilage, at the time of indentation, and the simultaneous disappearance of the fluid upon removal of the load. The fluid occupies over 70 percent of the articular cartilage. We could confirm that the exudation and inbibtion of the fluid from and into the articular cartilage was closely correlated with the deformation and with the lubrication mechanism of the articular cartilage. We also examined the deformation behavior of the articular cartilage under repeated loading. These findings should be of great help in the development of a new biomaterial which has all the fine mechanical properties of the articular cartilage and which can be used as artificial articular cartilage.

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In this biomechanical analysis, alumina ceramics was employed for the part coming in contact with the bone and the combination of HDP with alumina ceramics for the sliding part. For prevention of sinking and loosening, the femoral component was designed to be loaded on the cancellous bone at the distal end and the anterior and posterior cortical bone of the femur, the tibial plate was designed to be loaded on the plateau, and the posterior slanting surface of the tibial stem was designed to be loaded on the posterior cortical bone. In order to prevent the stem from rotating, small brims were provided on both sides of the stem. Since 1980, 120 knee joints have been replaced and clinical results have been excellent in all cases. Analyses on the stability of the tibial component inserted into the bone were made by means of three-dimensional FEM. The MSC/NASTRAN program was used. The numbers of solid elements, nodal points and degree of freedom were 1188, 1469 and 4100, respectively. Certain tibial bone conditions were assumed; namely, that the cancellous bone was relatively healthy (with Young's modulous of 100kg/mm^2) and remarkably atrophic (with Young's modulous of 10kg/mm^2), and that the subchondral bone was removed completely or partially. Four kinds of loading conditions on the plateaus were assumed; namely, (1) vertical loading on the medial and lateral sides, (2) on one side, (3) loading obliquely at an angle of 45°on one side, and (4) parallel loading to the plateau surface on one side. When the bone is healthy, a large amount of load is transmitted to the plateau. However, when the bone is atrophic, it is transmitted to the posterior slanting cortical bone from the stem. The posterior slanting surface of the stem plays a greater role as a supporting area. Even when the load is applied to the plateau on one side, the compressive load is kept between the plate and the bone on the opposite side. Under the severest condition, that is, when the load is given obliquely on one side, the stem as well as the brims prevent the component from moving anteriorly, rotating laterally, or tumbling. It is concluded that even under the severest condition, our designed tibial component remains quite stable on the tibia.

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The curved surfaces of knee joint condyles are rather complicated in shape, and these complicated shapes may have important roles in movement and load bearing in the knee. Thus, first of all, it is necessary to express the articular surface shapes in mathematical formulations in order to elucidate the joint movement mechanisms. Their mathematical expression, however, becomes complicated because these surfaces are made of rule-less free-formed shapes. However none of the pertinent research works has been performed in spite of the above-mentioned necessity. Therefore, we deduced an equation of curved surfaces to express the entire articular surface mathematically through the application of computeraided designing theory, which has been in use in automobile and other industries. In the measurement of the articular surfaces, we applied reconstructed silicon plastic models. After that, using the above-mentioned mathematical equation and the actual data, we computed differential geometrical variables and abstracted articular feature patterns. Further, we introduced the indexes of load-bearing capacity for the articular surfaces of contact, considering various knee flection angles.

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The feasibility of myoelectric control using the facial muscles, frontalis, temporalis, buccinator, and sterno-cleido-mastoid, was investigated. Tracking experiments were performed and compared with manual control manipulated by an on-off switch matrix. The subject was required to respond with appropriate muscle movement or to switch a key according to command, which consisted of five different numbers displayed on the CRT screen in random crder. Two experimental parameters, i. e., command display interval and time constant of an integrator circuit which was used to smooth myoelectric signal were varied. Finally, the rate of the subject's correct response was calculated every 10 miliseconds over the 10 time trials. Also, tracking error, delay time, and settling time were calculated for the evaluation of each control modality. The results showed that myoelectric control under the use of a smaller time constant gave a faster response than manual control, with some exceptions, despite the use of a pattern discriminator. On the other hand, manual control provided performance superior to myoelectric control at longer command display intervals. Total inspection of the results suggested that the myoelectric control offered tracking performance approximately comparable to manual control.

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Studies on artificial hands are done at many laboratories all over the world. The necessary functions for artificial hands hereafter may be dexterity, speediness, flexible handling, intelligence, and so forth. The playing of keyboards can be considered human activity which is highly dependent on these functions. This study aims to have an anthropomorphic robot play a keyboard (an electric organ in the first step of this study), with a focus on its degree-of-freedom mechanism and speediness, with the intent of developing artificial hands for more universal uses. The following three points are keys for the development of an anthropomorphic robot with the capability to play keyboards: 1) the integration of multiple degrees of freedom at the fingers, 2) the speed of finger and arm motions, and 3) the composition of a microcomputer system to control the mechanism for the multiple degrees of freedom. The design was to have 2 degrees of freedom for the thumb and 3 degrees for each finger, totalling 14 degrees, based on the analysis of motions of human fingers. As to finger driving units, it is impossible for actuators (DC sevomotors), which drive the multiple freedom mechanism, to be installed at the fingers. Therefore, actuators are installed in the body of the robot, and their power is transmitted through reduction gears to the fingers by wires and outer-wire tubes. Moreover, spring elements are introduced in the power transmission units to minimize the effects of friction forces between wires and outer-wire tubes on the responses of finger motions. Fingers are made of CFRP (Carbon Fiber Reinforced Plastics) to reduce the load on the arm. The experiments on a five-finger model have resulted in realization of 10 (Hz) tapping. In terms of an arm, the basic necessary data for design and control methods of an artificial arm were obtained through the analysis of human postures and of motions of the arm as a linking mechanism. The artificial arm is designed to be humanlike in size, shape, and functions, and to have 7 degrees of freedom including one redundant degree. Actuators are DC servomotors, sensors are velocity and position sensors, and the arm is made of CFRP, as are the fingers. Velocity and position control have enabled speedy, smooth motion of the arm. Concerning the computer system, a hierarchically structured multi-micro computer system has been composed, because total degrees of freedom are near to 50 when the degrees of freedom of four limbs are totalled. As a result, this robot system has realized the fluent play of tunes for beginners on a keyboard instrument.

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The load actuated brake knee for above-knee prostheses is very commonly used. This knee is useful in stopping knee collapse during stance. However, its braking effects during walking and its mechanical characteristics are not clear. Therefore, we undertook the following research: (1) Measurement of brake moment for various load actuated brake knees. (2) Measurement of knee moment with above-knee prostheses using pylon study. A physical testing device was produced and the relation between load and brake moment of the knee was measured. Brake moment was substantially different between various knees. Knee moment was measured by pylon study on four above-knee amputees during their walk on 1) a leveled floor with standard alignment stability, 2) reduced alignment stability, and 3) descending ramps, all both with and without load actuated brake knee. At the moment of heel contact, knee stability is gained by alignment stability and the action of hip moment, but the load actuated brake knee does not play any role. The load actuated brake knee can prevent knee collapse at the beginning of the stance phase, but at the same time interferes with knee flexion at the end of the stance phase.

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The purpose of this study is to establisha manufacturing method for a cosmetic cover. At present, the kinds of cosmetic cover are limmited because the technics have not been made progress in these 10 years. Even in the biggest prosthesis shop in Japan, the classes of cosmetic cover are 9 for male, 5 for female and 7 for children. Therefore, most handicapped persons are dissatisfied with its form. The character of this study is to measure a residual hand of handicapped person automatically, secondly is to manage the measured numerical values, and finally is to mill a model for the affected hand with the measured and managed results by the same set up. Consequently, this study has been advanced to lay stress on the following developments. 1) 3-dimensional drive machine and computer hardware. 2) Touch sensor for the living body. 3) Software for the automatic measurement. 4) Software for the data management. 5) Software for the milling. As the results, we can manufacture a symmetric cosmetic cover for the residual hand easily, Besides, the utility became possible in the rehabilitation field.

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Usual artificial legs are made relatively simply in order to give an impression of safety. Thus, the functions of these legs are not usually sufficient to provide a satisfactory walking motion, and users are compelled to walk at a limited speed and with a suitable gait to use artificial legs. Users want artificial legs that are much more easily operated. To respond to this request, developments of powerdriven and sentient legs have been investigated. However, even if the newest scientific techniques are applied, the practical applications of these legs seem to be very difficult. Therefore the authors consider that the first step must be done from the point of improvement in the mechanism of artificial legs. One of the authors has already reported analytical results about human walking motion. It is known from these results that human walking motion is done very reasonably to maintain dynamic stability and to lower fatigue during motion. We have tried to improve the mechanism in the artificial leg according to our knowledge about human walking motion in order to make the activity of the artificial leg closely approach that of the human leg. With regard to motion around the ankle during stance, the relation between the moment M about the ankle and the joint angle θ at the ankle can be approximated by a spring action. Thus, we made an ankle joint having a dorsi flexion function and a plantar flexion function and we added a rubber spring to the ankle. In addition, we gave the ankle a function of valgus and varus. It was experimentally confirmed that these devices make a jogging motion and a walking motion across a slopeway smooth and very close to human motion. The experimental results of floor reactions showed that the newly developed foot has a much better function than a SACH foot. With regard to the knee joint, the most important problem is to prevent giving way. An equation of condition for the prevention of giving way is derived in this paper. A friction lock mechanism was improved according to this equation, and it was experimentally confirmed that the new mechanism produces a much greater locking force than usual mechanisms. The second important problem is to reduce the shock produced when the heel contacts the floor. To absorb the shock energy, we also added a rubber spring to the knee joint. The usefulness could not be clearly confirmed by experimental results, but the walking motion was smooth in both ascending and descending the slopeway.

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For a leg amputee, the first step of rehabilitation is to be fitted with a prosthesis. Present leg pros-theses are too simple to fulfill various demands of a wearer such as changing walking speed, walking up and down stairs, and so on. One of the courses of research undertaken by many laboratories in this field is to make an intelligent prosthesis. The aim of this paper is to describe the development of an intelligent passive above-knee prosthesis that can automatically adapt dynamic parameters to various walking situations. This prosthesis is intended to achieve an optimal knee flexion movement controlled by the suitable valve adjustment of a pneumatic cylinder unit with a microcomputer system. The unit is attached across the artificial knee joint. To provide the basic behavior of the prosthesis with the unit, a mathematical model has been built for the unit and the prosthetic system. In addition, thigh and shank angular displacements of various walking situations of sound gait have been measured. Mathematical calculations were made to determine the suitable valve adjustment to simulate the sound knee flexion movement at various walking speeds and walking downstairs with a pros-thetic gait. It was proved that the dynamic valve opening and closing during the swing phase provides suitable control. Prosthesis evaluation was fabricated. A portable one-board-microcomputer system was employed as a control system and CO_2 gas from a portable gas cylinder was used as a power source of valve movement. These two and gas regulators were backpacked. A miniature electro-magnetic valve and a diaphragm cylinder were attached within a pros-thesis so that an intact computer-controlled pros-thesis was achieved. Two A/K amputees were fitted with this pros-thesis and underwent examination walks. They succeeded in changing speed when walking. It was proved that the valve adjustment should vary according to the wearer. It is also suggested that, the iterative calculation should be done to seek the optimum valve adjustment. The first valve adjustment is calculated with the input of thigh angular displacement of sound gait, but the second and following ones are calculated with the input of that of prosthetic gait. It is expected to be possible to obtain the optimum valve adjustment by repeating this procedure. This paper proposes one of the possibilities for the coming generation of A/K prostheses.

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This paper deals with the development of an A/K prosthesis that is able to regulate its knee-jointtorque automatically according to walking period. First, the development of the new A/K prostheses WLP-5 and WLP-6 are discussed. From the results of a simulation analysis of the movement of the A/K prosthesis during a swing phase. The necessity of a little driving torque around the knee joint at the beginning of the extention was designated. The A/K prosthesis that had the following two mechanisms were performed. 1) A mechanism to change its damping torque around the knee joint according to walking period. 2) A mechanism to generate a little driving torque around the knee joint by self-accumulated power. From the walking experiments by the amputees, It was confirmed that a wide range of walking period (1.1〜1.5sec) was possible for them by wearing the WLP-6 system. Second, the approach to prediction of the walking period of the next step using EMG is discussed. A surface electrode and an electronic circuit for processing EMG were developed. A new method of composing EMG data having the effect of Hi-pass filtering was introduced, and its effect was verified theoretically and experimentally. The prediction-algorithm of the next step's walking period using EMG was introduced. From walking experiments by the amputees, it was verified that the next step's walking period could be precisely predicted.

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It is estimated that in Japan there are over 48,000 people who have lost their legs due to on-the-job accidents, traffic accidents, disease, etc. Since our legs have the important functions of supporting our body weight and carrying us from place to place, such people are severly handicapped in daily life. To help them, lower limb prosthesis without actuators are conventionally used. However, the conventional A/K prosthesis have some defects: amputees cannot smoothly go up and down stairs, cannot intentionally change walking speed, and so on. In order to improve the function of the conventional A/K prosthesis, we are developing an active A/K prosthesis through a project supported by the Ministry of International Trade and Industry. First, this paper deals with the design of the prototype model of the active A/K prosthesis and the evaluation of its performance. The model is equipped with a hydraulic actuator (RSA) in the knee joint and foot sensors made of conductive rubber in the sole. The nominal output torque of RSA is 118Nm, and the oil pressure is 9.8MPa. The RSA is controlled by a microcomputer which determines the stance/swing state according to the signal of the foot sensors and generates the position pattern of the knee joint to match the gait motion. The microcomputer consists of an 8-bit CPU, AD converters, and DA converters. In testing, amputee subjects had no significant difficulty in going up and down stairs regardless of various step heights. This result shows the control scheme applied to the model is effective for active A/K prosthesis. In the next stage, we aim at reducing energy consumption and at miniaturizing the total system, including the hydraulic power unit.

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This paper describes the control of an active exoskeleton for the lower limbs, which is a kind of motorized orthosis for the locomotor handicapped such as paraplegics. This active exoskeleton supports the body of the patient and has electrohydraulic servo actuators to motorize his or her hip and knee joints. Foot switch sensors and ultrasonic sensors are introduced in this locomotor system to furnish the sole contact signal and the angle of the body of the vertical axis. A microcomputer with special hardware controls thus constitutes the active exoskeleton. In order to generate a gait pattern, a normal pattern taken from a normal subject is prerecorded. However, the frequency characteristic of the active exoskeleton is not sufficient to track the normal gait pattern. To improve the trackability based on the periodicity of the pattern, the input signal is regulated so that the output pattern of the active exoskeleton may be as similar to the normal gait pattern as possible. This new input signal is used at the next gait cycle, and the output gait pattern asymptotically approaches the normal one with walking. Experimental results show that this method is useful as long as the normal gait pattern is periodical. A control method for stable gait is presented by using a 5-link model where there is no torque at the ankle joint. A normalized gait pattern is composed based on normal human gait. The modification for an asymptotical stable gait depends on three state variables of the active exoskeleton: ratio of play back time to a step period, angle, and angular speed of the center of gravity. Using the three state variables, a three-dimensional table for the gait stability is obtained by computer simulation. The normalized gait pattern is modified in amplitude and playback speed according to the parameters indicated in this table. The special hardware preforms the pattern modification to improve the processing time sending it to the servo system. To make certain of the stance phase, the playback start for this phase pattern is synchronized with the heel contact of the corresponding foot. When the swing phase is performed, the controller verifies whether the foot in that phase strikes the ground or not. If heel contact is not made, the gait pattern for the next phase is inhibited. In consequence, there is no danger of flexion of the knee during the support phase. Experimental results with a normal subject show the feasibility of asymptotically stable motorized level walking although control is assured only in the sagittal plane.

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ヒトの立位姿勢の調節系における体重心位および床反力作用点と下肢筋筋電図の関係を,1)身体を足関節まわり前後方向にゆっくりと動かした場合2)音信号に反応して速く動かした場合について調べた.実験結果を台付き単一倒立振子モデルを用いて解析した.さらに足底からの感覚入力の姿勢調節系への関与の程度を知るため,足関節上部こ駆血帯を巻き虚血性神経ブロックを行なった.なお本論文では運動に伴う上半身の影響を減ずるため被験者に前屈位をとらせた.一定の姿勢(後傾位と前傾位の間で)を保持させた場合またはゆっくりと身体を足関節まわりに動かした場合,下肢筋筋群筋活動と体重心位のリサージュと床反力作用点とのリサージュはほぼ同一のパターンを示した.前傾するに従い下腿三頭筋の活動量はほぼ直線的に増大するが,後傾位ではほとんど筋活動はみられなかった.前脛骨筋は逆に後傾位になるに従って活動量が増大し前傾位ではほとんど筋活動はみられなかった.身体の速い運動では運動開始時の体重心位に従って前脛骨筋(TA)と下腿三頭筋(GC)の活動に合目的的な筋活動の切り替えがみられる.これによって前方または後方へのモーメソトが有効に作り出され,運動が遂行されることが示された.中立位(TAに活動がみられずGCに軽度の活動がみられる姿勢)から最大前傾位まで身体を動かした時,三相性の筋活動-GCの休止,TAの発火,GCの再発火-がみられた.後傾位から中立位まででは二相性の筋活動-TAの発火増大,GCの発火-がみられた.速い運動時にみられる床反力作用点軌跡の逆応答は,この下肢筋筋群の筋活動によって作り出される足関節まわりのトルクを反映していることが,モデルの解析から明らかとなった.この現象は前脛骨筋,下腿三頭筋の単収縮時にみられる体重心位と床反力作用点の関係から確かめられた.駆血後30〜40分目で拇趾球部の表面感覚は30%以下に低下した.身体の前後方向の可動域は開眼・閉眼でともに駆血前の約70%に減少し,中立位から前傾位までの速い身体運動では前傾位でとまることができず被験者は転倒した.足底からの感覚入力は下肢筋筋群の活動量および運動遂行のための筋電パターンに重要な働きをしていることが示された.

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Even when humans stand in a comfortable posture, their center of gravity fluctuates constantly. Many researchers have been studying this phenomenon in various ways since the 19th century. The fluctuation of the center of pressure under the foot has been measured by using a force plate. Many results have already been reported, but most of them discussed static measures, such as mean position and standard deviation, of the fluctuation. Some of them have paid attention to the power spectrum and the correlation function for the measured fluctuation, and analyses with a computer are increasing. For this purpose, data should be collected appropriately. A few researchers, including the authors, have considered that the fluctuation of the center of pressure can be assumed to be a random stochastic process. Therefore, the autoregressive model is applicable to the representation of its dynamics. In this paper we show how to apply the two-dimensional autoregressive model to data measured by two force plates. Moreover, we investigate the adequate sampling rate and the number of data based on a statistical method. The main results are as follows: (1) The sampling rates which were suitable to measure the statistics of the fluctuation were obtained according to the conditions of standing posture. (2) Suitable sampling rates to analyze the power spectrum and correlation function were obtained. (3) A statistical test showed that almost all the measured data were stationary with respect to the standard deviation. (4) The estimated AR models were able to reproduce the characteristics of the measured data qualitatively when we applied the two-dimensional AR model to the measured data, the number of which was 512.

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Few studies on the rotation of the spine in vivo have been reported for lack of a reliable clinical measuring system. In this paper, the method of measuring trunk rotation in vivo is presented. Special devices were made in order to measure movements of the head, the first thoracic segment, and pelvic region in 2-dimension. LEDs were positioned on both sides of the head, the first thoracic segment, and the pelvis. The movements of rotation of the cervical region and thoracolumbar region were measured by SELSPOT SYSTEM. The study was performed on 20 normal young males (24-35 years), 15 normal aged subjects (62-85 years), and 23 hemiplegic patients (52-78 years) including 9 left and 14 right hemiplegics. The mean range of the total spine rotation was 254 degrees and 239 degrees in young males, 184 degrees and 180 degrees in the aged subjects, and 169 degrees and 149 degrees in hemiplegic patients in sitting and standing positions, respectively. The mean range of rotation in the cervical region was 147 degrees and 133 degrees in young males, 120 degrees and 116 degrees in the aged, and 110 degrees and 96 degrees in hemiplegic patients in sitting and standing positions, respectively. The mean range of rotation in the thoracolumbar region was 114 degrees and 113 degrees in young males, 69 degrees and 68 degrees in the aged, and 65 degrees and 59 degrees in hemiplegic patients in sitting and standing positions, respectively. It is apparent that the range of rotation of the spine decreased as a function of age. The decrease is marked in the range of the thoracolumbar region.

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In a study of the human gait, it is important to know about variations in stride. The author has formulated a measurement system of stride during gait by using an ultrasonic technique. This measurement system is composed of a pair of shoes, a device that measures human gait stride, and a microcomputer. Each shoe has an ultrasonic wave radiator attached to its toe, and an ultrasonic microphone to its heel. The device for measuring stride was made from a digital circuit assembled with CMOS IC. This device is 650g in weight. The measurable time for one battery charge cycle was about 4 hours. Output signals of this device are serial electric signals with CMOS level, serial optic signals by LED, and audio frequency shift keying signals in the form of RS 232 C standard. The user can select one of these output signals and collect them on the diskette of a microcomputer. As a result of the experiment, the following conclusions were obtained: 1. Measureable distance from the right toe to the left heel or from the left toe to the right heel was up to 700mm. 2. This system measures only one-dimentional distance; however, the dynamic variations in distance during gait are measurable except for a period when one leg is passed by the other. 3. This system is useful for outdoor working.

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A personal computer-based system for walking analysis is shown. The system, which is both portable and low in cost, is constructed with a personal computer system and two measuring subsystems with a microprocessor for measurement, communication, and control. For data acquisition and processing, a personal computer-based acquisition system has been used. The sampling rate of the system is 60 frames per second. One of the measuring subsystems uses equipment for measuring pressure distribution under the foot. The sensor for measuring pressure distribution under the foot is composed of a 0.3mm thick anisotropically electroconductive silicon rubber sheet (AF sheet) that is sandwiched in between the matrixed upper and lower electrodes. The sensor is inexpensive and easily attachable to the foot. Dependence of the hysteretic characteristics of the sensor cell on applied loading frequency and maximum applied load are measured with a trial device for measuring dynamic characteristics. Then the sensor is represented as a three-parameter model consisting of a Maxwell element in parallel with a spring. The other measuring subsystem uses equipment for the detection of marked point locations for kinematic analysis. Five lamp markers are attached on anatomical landmarks of the subject, who is tracked by Saticon camera. The marked point location digital data are memorized in real time by a personal computer through the marked point detector and ring buffer memory. Results for human walking experiments on both floor and treadmill have been shown.

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Hip and knee joints, while walking, make three-dimensional movements comprising X, Y, and Z axes. Angular changes while walking are repre-sented by treatment with a microcomputer using three electric potentiometers orthogonal at these three axes. The time passed from one heel contact to the next is normalized to 100%, and the angular change within ten seconds is over-written (normal hip joint flat gait). Stance phase and swing phase have predominantly those movements in the direction of extension, adduction, and internal rotation and in the direction of flexion, abduction, and external rotation, respectively (normal knee joint flat gait). The stance phase has small movements, with increased movements proportional to the rate of gait; while the swing phase has a peak of flexion, abduction, and external rotation (joint angles up and down stairs). Both hip and knee joints have more variations in movement (hemiplegic patients). Angular changes are represented by scissor's gait, circumduction gait, stiff legs, etc., in addition to differences between left and right movements (ataxia). Hip joint angle is most stable at 90 steps/m, with more variations at 40, 60, and 120 steps/m, which makes an index to the determination of optional rate of gait.

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Measurement of dynamic force distribution under the foot is discussed for the purpose of dynamic analysis of foot function in walking. This method is expected to bring various beneficial information about foot function because the foot is always exposed to great pressure in standing or walking, and foot deformities or pain can be assumed to be the result of this great force. Some basic problems are studied here concerning the dynamic force distribution pattern drawn by the foot in walking, the production mechanism of this pattern, and the relation between this pattern and the skeletal structure of the foot. The first finding was that in all 17 subjects the pressure moved constantly from the heel to the medial part of the forefoot and the great toe through the lateral part of the forefoot. This constant moving pattern can be thought to be the clinical standard for the functional estimation of foot disorders. An example of functional estimation of postoperative club foot disease is shown to point out the effectiveness of this estimation. Moreover, the peak pressure on the second metatarsal head is the greatest in the forefoot, and the so-called anterior arch is thought not to exist at least when great pressure is loaded on the forefoot. The second finding was that the phenomenon of the pressure once going round from the lateral to the medial part of the forefoot is caused not by the skeletal structure but is the result of the control involved in walking. In other words, this phenomenon can be explained by the movement of the center of body weight from one foot to the other during the propelling period. This finding can be utilized for the estimation of walking control abililty, and a case of Charcot-Marie-Tooth disease is discussed. The last finding was that the great toe does not actively push off the floor, because even if the great toe is fixed in a fully dorsal flexing position, the pushing off force obtained by the force plate does not change. The greatest pressure is seen on the great toe in the propelling period. These two opposite results can be explained by the "windlas mechanism." Namely, the tension of the plantar fascia according to the dorsal flextion of the MP joint firms the medial longitudinal arch and simultaneously extends the MP joint by the reaction force of the plantar fascia. A simple model is proposed to calculate the plantar fascia reaction force, and this force is proved to attain up to 67% of the body weight. This great force is thought to be the mechanical cause of hallux valgus.

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In this paper, we deal with the activities of muscle groups about joints concerned with walking motion. Several mechanical properties of muscle activities during walking motion are clarified by the analytical results of experimental data. These results are confirmed by considering their correspondence to the physiological appearance of muscles. Muscles are classified into 1-joint muscles and 2-joint muscles. It is considered that the latter particularly contribute to dynamic stability during motion. However, equations of motion of each element of the leg are concerned only with the sum of all muscle activities which operate the element, so that to separate the activities of 2-joint muscles from the total is impossible. In some approaches, assumptions have been made on the spending of energy during walking motion or on the synchronizing of the complicated activities of muscles. However, it seems that these assumptions have rather lowered the reliability of solutions. We tried to clarify the activity of each muscle group by analyzing the observed results of human gait and the change of moments about joints. First of all, we investigated what motions of elements are respectively produced by moments about the joints of the hip, knee, and ankle at each second and which functions among those of spring, damper, and motor work at each second. Then we investigated how the moment about one joint relates to the moment about another joint. Thus the activity of a 2-joint muscle is found and then that of a 1-joint muscle is obtained. Results are summarized as follows: It was found that fatigue is almost evenly averaged over all muscle groups because power is skillfully distributed to each muscle group, and the energy loss during walking motion diminishes because of sufficient spring action. It was also found that the control of muscle action is very simple, different from the usual opinion. The spring action of muscles and the skillful action of 2-joint muscles provide suitable motion as a quick response to conditions of road surface in spite of the simple control mechanism. Further, it was found that the stretching and the contracting velocities of muscle actions are respectively constant, and it is suggested that the muscle activities may be controlled in response to strains produced in bones. These results give not only a new understanding of the human body, but also important suggestions for designing delicate machine motions.

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Mathematical model analysis was carried out on the gait of patients with hip diseases in order to clarify the patients' gait characteristics which were not obtainable by usual techniques. Motion in the sagittal plane was noted, and a two-dimensional mathematical model developed by Yamazaki was used. For the anthropometrical measurements, 'contour maps' were used bucause patients' body proportions were different from the norm. Displacement was measured by PSD camera simultaneous to floor reaction force measurements and these were transmitted to mini-computer by on-line real-time processing. Subjects were 17 patients with hip osteoarthritis (11 for total hip replacement, 1 for hemi-prosthetic reconstruction, 3 for osteotomy, and 2 for arthrodesis of the hip); 4 normal subjects were measured for control. Joint moments, muscle forces, and joint reaction forces were assumed by mathematical model analysis. In order to investigate the validity of measurements and analysis, joint reaction forces of normal subjects were compared with results of other researchers and good agreement was obtained. For the patients with total hip replacement, the maximum value of hip joint reaction force was almost the same as that of the normal subjects, but the duration for which the large force was transmitted was longer than for normal subjects. Also, it became evident that the large force was transmitted to the knee joint in the push-off phase. These were common characteristics of patients for hemi-prosthetic reconstruction and osteotomy, and it can be said that they provide compensation for the instability of hip and knee joints. In patients with arthrodesis of the hip, the maximum values of reaction force with contralateral hip joint and bilateral knee joints revealed about twice the normal value. Thus, it is evident that it is necessary to discuss the durability of these joints when the procedure for arthrodesis of the hip is applied.

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In human bipedal walking, body segments act in harmony with each other. However, both the human body and bipedal walking are unique among other primates and other terrestrial animals. Therefore, some explanation must be offered for this uniqueness. It seems correct to state that there are some mechanical relationships between the human body and bipedal walking. Body motions are achieved by opposing muscular efforts against gravitational force, but basic daily motions such as walking should be performed to minimize energy consumption. One feasible solution which minimizes muscle effort is the coinciding of the motion pattern with the vibration mode of the system. In this study, bipedal walking was mathematically modeled as a coupled vibration system of body segments. The mathematical model was a three-dimensional model with the following components: head, thorax, pelvis, arms, thighs, shanks and feet. A spring and a dashpot are attached against the relative rotation between thorax and pelvis, and also between thigh and shank. The spring element of the knee joint was a nonlinear spring to avoid hyper-extension. Sagittal and vertical forces at the pelvis segments, and moments at the waist and hip joints were applied as external forces. Accordingly, the vibrations of body segments were expressed by a 10th simultaneous second-order differential equation. The numerical calculation was performed using the 4th order Runge-Kutta method. The vibration mode of the experimental link model was measured by a 16mm cine camera. The experimental results agreed with the results calculated from the same morphological constants of the link model. As a result, the following close relationships between the human body and bipedal walking were found: (1) adequate viscoelasiticity at the waist joint is required for effective walking, (2) human morphological body balance is matched for smooth and harmonious bipedal walking. The method of this study will be able to be utilized for the evaluation of artificial legs or the estimation of the effects of orthopedic operations.

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