The present study aims to estimate the force of stretch reflex origin (short-latency and long-latency reflex) separately from measured stretchevoked force with the aid of a mathematical muscle model, and to examine the extent to which the brain can modulate the reflex in different tonic forces and in different kinds of instructions given the subject against mechanical perturbation. A small ramp stretch was applied to the human flexor pollicis longus muscle at an unpredicted time while the subject maintained a constant flexing tonic force. The amount of stretch was 2.4 degrees and the duration of stretching was 15 msec, which were both identical in all the experiments. The instructions given the subject prior to the experiment were either "let go" or "do not react" or "resist." The results are summarized below. (1) The force developed by the short-latency reflex (SR) commenced approximately at 35 msec after the onset of stretch and the force by the long-latency reflex (LR) at approximately at 60 msec. The voluntary reaction time, which depended on the subject, ranged from 117 to 172 msec. (2) The response of the stretch model agreed closely with the measured force during the period of 35 msec just after the onset of stretch, which originated only from the muscle viscoelasticity and passive components such as skin, joint and moment of inertia of the thumb. (3) The force of SR and LR was estimated by subtracting the viscoelastic force of muscle (model response) from the stretchevoked force. (4) The force of SR was averaged during the period from 35 to 60 msec, and the force of LR from 60 msec to the voluntary reaction time. The averaged force is defined as the reflex responsiveness. (5) Both reflex responsiveness of SR and LR increased with an increase in tonic force. (6) Reflex responsiveness of SR and LR were 18% and 75% of the stretch-evoked force, respectively, under the instruction "do not react." (7) Reflex responsiveness of SR did not change significantly at the same tonic force with varying instructions. This suggests that neither the muscle spindle gain nor excitability of the alpha-motoneuron pool can be modulated by the brain in costant tonic contraction. (8) Reflex responsiveness of LR was greatest in "resist," which was approximately 90% of the stretch-evoked force, and smallest in "let go," which was approximately 15% of the stretch-evoked force. (9) These results imply that the stiffness of motor servo can vary with tonic force and instruction, and that the stretch reflex, in particular, LR, would assist in regulating the muscle length with muscle viscoelasticity. Further, reflex gain of the transcortical path or spinal poly-synaptic path can be modulated according to the instructions given the subject by the brain.

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Most daily motions of the upper extremities are performed in regular patterns in spite of the possibility of various motions under greater degrees of freedom. This fact causes us to expect the existence of some criteria for determination of unconscious motions. Clarifying the criteria would be useful not only to improve manufacturing operations and sport activities or to plan medical care for pathological motions, but also to design a controller for mechanical manipulators. In this paper, we assumed that the criteria depend on the internal energy expended by muscles and ligaments. Six energy elements such as visco-elastic energy were defined from the physiological characteristics of soft tissues. The total criterion was expressed by linear combination of the energy elements. The muscle forces involved in the energy elements were estimated by the computer simulation technique. The mathematical model of the upper extremity was constructed by four rigid segments connected by ball joints. Nineteen muscles were considered to control the segments. By using mechanical equilibrium equations of the link system, we can calculate joint moments by referring to measured joint motions. The joint moments must be exerted by muscle force. However, because of the lack of equilibrium equations between joint moments and muscle forces, we estimated the muscle forces by applying the minimal principle of the sum of the square errors between joint moments and muscle moments and between the estimated muscle force patterns and the measured electromyographic patterns. Three-dimensional joint motions were measured by two sets of infrared detective cameras. Free and restricted reach motions of eight persons were analyzed. Consequently, it was found that the viscosity element of soft tissues has great influence in determining the motion path. The result can be expressed in another way: that the unconscious motion path is determined to minimize the sum of the amplitude of joint angles because the motion time does not change so much among various paths. There are optimum values regarding velocity, direction and starting height. The optimum value of velocity is determined to minimize the muscle power element, and those of direction and starting height are affected by both the joint viscosity element and muscle power element. In these results, individual differences can be neglected. The criterion expressed by the resistance of joint and muscle viscosity is a new idea for motion determinants.

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Very fast forearm extensions and flexions toward a visual target within the horizontal plane were investigated. The subjects initiated the movement with maximum effort from a fixed position on hearing a short tone stimulus. In the first experiment, during some movements, target location changed suddenly, thus requiring an intentional correction of the trajectory by the subject. The subject knew the first target location well before the movement was initiated but he did not know when and to where the target position would change. Changes of target location during the reaction or movement time generally elicited movement to the first target, followed by movement to the second one after varying reaction times. The reaction time R_S to the sound command which initiated the movement to the original target was affected by change of target location and decreased by about 25-50 msec when the time from the presentation of the auditory stimulus to change of the target (ISI, interstimulus interval) was -200 msec to -50 msec. And in this range of ISI some of the movements were initiated directly toward the new target. The reaction time R_L to change of target location was a function of ISI: when ISI<150 msec R_L correlated negatively with ISI and when 200 msec <ISI<550 msec, R_L was a little longer than the simple visuomotor reaction time. The movement that initially progressed toward the first target could never begin to deviate toward the second one untill it passed the negative peak of acceleration. In the second experiment, movements were also initiated in response to a tone command but the visually presented target disappeared during some trials at various instants, The subjects were instructed to continue the movement toward the original target location even after target disappearance. The final position reached was a function of target location and time of target disappearance: for a distant target the angle of the final position decreased with time after target disappearance while for a near one it increased with time. This result suggests that the centrally stored target location changes with time if the target disappears. On the basis of the results of the present and previous studies on the fast positioning movements, a model of the forearm movement control system was constructed. It can explain the different modes of the movement control process, the relations among subsystems participating in movement control and movement modification in response to location shift or disappearance of the target.

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This paper deals with relation between the stress of the finite element femur model and femoral morphological parameters. First of all, three-dimensional geometry of 42 human femurs (21 males and 21 females) was reconstructed numerically from photographic data in three different directions. These original data were used for finite element representation of the femur geometry, for determination of external load environment around the bone and also for calculation of characteristic morphological parameters of the whole bone shape. Finite element models of the femur were subjected to Integrated Structure Analysis System 2 (ISAS 2) under calculated load conditions with published material properties. Factor analysis was applied to calculated stress data, morphological parameters and load conditions. The following relations were found. (1) Equivalent stress on the diaphyseal surface is intensively influenced by bone thickness but it is never affected by a general size factor. (2) The direction of maximum equivalent stress on each cross section is related to neck torsion but the rotation of the maximum stress direction is not so closely related. (3) The inclination of the stress along the shaft on the medio-lateral margins is influenced by lateral leaning of the femur. (4) There is a sexual difference in the interaction between bone thickness and equivalent stress but the mechanism is not yet understood.

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Time series of pain sensation thresholds are analyzed by the time series analysis technique. Mechanical stimulus, indentation of a needle on the skin, was used for pain stimulus. Subjects were healthy male and female humans. Stimulation was done for one minute, and time series of pain sensation thresholds were obtained. First, the trends of pain thresholds for 50 minutes were analyzed by regression analysis. First-order coefficients of first-order regression showed, on average, that pain thresholds tend to increase about 0.2 or 0.3% per minute. Second, frequency of the time series of pain thresholds was analyzed. Autocorrelation functions suggested that there exists periodicity in pain thresholds. To confirm this, alternative stimulation with a pin and cylindrical needle was done. Cross correlation showed that these were highly correlated, and it was considered that there are periodical factors in pain thresholds. The periods of the peak value of the power spectrum of pain threshold time series were obtained from fifty experiments. This showed that pain thresholds fluctuate periodically during about 10 minutes. As periodicity of pain thresholds was found, factors which produce this phenomenon were investigated. From the gate control theory, it was supposed that such fluctuations of pain threshold were caused by the inhibitory effects of touch or pressure sensation. To investigate these effects, pain thresholds and touch thresholds were measured simultaneously. Cross correlation and the coherence showed that there was a positive correlation between pain and touch sensation. This suggests that the periodicity is not caused by peripheral inhibition effects in the spinal cord but is caused by the higher central nervous system. In order to infer the conditions of the brain, several physiological parameters were measured. They were alpha rhythm・beta rhythm・theta rhythm from EEG, EMG, heart rate and skin temperature. Experiments were performed for 100 minutes. A two-dimensional autoregressive model was introduced to the analysis. Each physiological parameter was regarded as the input signal, and the pain threshold was regarded as the output of the system. For evaluation the relative power contribution was used, which is the ratio of the contribution of input signal to the spectrum of the output. For all physiological parameters, the relative power contribution was less than 50%. When focused on the main period of pain threshold which is about 10 minutes, the relative power contribution of theta rhythm had its peak at this period though values were low. From this result, as theta rhythm appears at the early stage of the sleep, there is a possibility that some periodicity of drowsiness causes the fluctuation of the pain threshold.

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Recent results of cognitive science suggest that learning is understood from three viewpoints: knowledge acquisition, representation and utilization. This paper studies, based on such an understanding, the learning of a robot manipulator with seven degrees of freedom for avoiding obstacles in the working space. The kinematics of the manipulator was represented by Denavit-Hartenberg's notation. For the knowledge acquisition to control, the minimization strategy of a potential function was employed. The potential function was defined as a sum of a quadratic form of state error vector and the penalty function; the former stood for the problem without an obstacle and the latter for a barrier yielded by existing obstacles which are mathematically defined as primitives like cuboids, cylinders and so on. In our studies, the learning process for manipulator motion is considered as a sequential change of knowledge structure. For implementation of such a scheme, an adaptive production system was used. The knowledge was represented in the form of production rules and could be modified by adaptation as a generalization or specialization. These rules were stored in a discrimination net for fast computer retrieval. The manipulator was implemented as a geometric simulator on a micro-computer and the production system by Lisp 1.9 on a large-scale computer. Simulation results were presented with computer graphics.

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The quadrupedal locomotion of three infant chimpanzees was studies and compared with that of two semi-adults. The posture, footfall order, phase duration, speed and foot force in locomotion were measured by means of the force plate and a 16-mm cine camera or video tape recorder. The infant animals moved freely without any attachments on the body. In ontogenic walking of chimpanzees, no clear trend was observed to change from the usual terrestrial pattern to the primate pattern. The free locomotion of chimpanzees from infancy to the semi-adult stage varied considerably. The ontogeny of quadrupedal locomotion in chimpanzees, starting with the four-limb standing position, to two years of age was divided into the following stages: 1) From two to three months of age: Beginning with the four-limb standing position and progressing to gliding advancement on the hands and feet. The forelimbs carry a larger part of the body weight than the himdlimbs during static standing posture. "Fist" walking is seen. The hip, knee and toe joints were always flexed. 2) From four months of age: The two diagonal limbs were simultaneously in the air while walking. Footfall order started. Stance phases were long. The step length was short. The foot was not placed near the position where the hand on the same side was placed. The cycle duration was long. The hindlimbs' maximum downward peak showed a significantly larger magnitude than the forelimbs'. 3) From six months of age: Constant and steady walking. The relative speed was slower in this stage than in older ones, if comparison was made between walks of the same cadence. When the equal relative speeds were compared, the accelerating maximum value of the hindlimb was larger in this stage than in older ones. 4) From nine months of age: "Knuckle" walking started. The step length became long. The cycle duration was short. The foot was placed on the outer or inner side of the hand on the same side. Stance phases became short. 5) From one year of age: The hindlimbs carry a clearly larger part of the body weight than the hindlimbs during the static standing posture. The relative speed was fast. Walking as well as galloping was included in the repertoire of quadrupedal locomotion. The hip, knee and the toe joints were extended. 6) Around two years of age: The animals were very active. The "crutch" was included in quadrupedal locomotion.

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The present paper deals with an automatic measuring method with a three-dimensional coordinate measuring machine for the foot. The objective in measuring foot shape is to design a good shoe model to make fitted prosthetic devices and to evaluate foot shape in orthopedic surgery and rehabilitation fields. To measure a soft and complicated object like a foot, a measuring method with a three-dimensional coordinate measuring machine yields good results. We developed a new micro-computer-based measuring system which can measure any complicated object exactly and automatically, can operate the measured shape to match many purposes and can manufacture that positive or negative model. Therefore, this system can be called a CAD/CAM system for the living body. This measuring machine has five axes (three degrees of freedom and a rotation structure for its sensor probe with two degrees of freedom). A capacitance-type touch sensor with a needle probe is used to obtain an ON/OFF touch signal. The main problem is how to measure a foot automatically. For such a complicated object, control of five axes is very difficult. A new automatic measuring method measures a foot model with simple measuring probe path data and then generates optimized path data. With that data, a foot can be measured automatically and efficiently. The next problem concerns data operation. One of the merits of this system is that it expresses a measured shape with numerical three-dimensional values. A connecting index to connect the measured parts smoothly and a bending curve to correct the measured shape have been developed. These are fundamental methods for the living body. With these measuring and data operating methods, a foot shape can be measured, and various shape operations can be done freely. To make a good shoe model or a fitted prosthetic device, the most important thing is to measure foot shape exactly and fully, with useful operating methods. Now these fundamental methods have been developed. This system is quite useful in shortening design time, because designs are fine tuned numerically, and can be optimized without constructing a test model.

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Shapes of motor unit action potentials (MUAPs) of the same motor unit (MU) changed obviously during contractions of muscle, in particular, when the limb was moving. Effects of electrode geometry and configuration on the shape of MUAPs were examined. On the basis of the results, an arrayed (five channel) surface electrode in a bipolar configuration was devised by which MUAP trains could be identified reliably even during limb movement as well as during isometric contraction. EMG activities of human biceps brachialis muscle were measured in voluntary isometric and isotonic contractions with the electrode, and inter-spike intervals of MUAP trains (firing rates) of the single MUs were calculated. The results are summarized below. (1) Shapes of the MUAPs were not affected significantly by the size of a rectangular electrode ranging from 2 to 8mm in both width and length. (2) As the inter-electrode distance of the bipolar electrode became shorter, the duration of measured MUAPs became shorter. This means that shorter inter-electrode distance makes it easier to distinguish accurately the activity of single MUs. (3) Configuration of a 5-channel electrode which made it reliable to identify MUAP trains was determined; three channels were placed in parallel with the muscle fibers with the distance between channels being 10mm. The interelectrode distance was 5mm and the disc electrode diameter was 2mm. Two additional channels were oblique to the muscle fibers. (4) MUAP trains of the single MUs were identified up to 20-40% of the maximum voluntary isometric contraction with the arrayed electrode, and the firing rates were measured. Firing rates of single MUs increased with muscle force. (5) EMG activities were measured in voluntary isotonic contraction over the range in loadtorque from 0.6 to 3.7 Nm and in elbow-flexion velocity from 0 to 30 deg/sec, and then firing rates of single MUs were measured. (6) Firing rates of single MUs were not significantly dependent on the elbow angle in the isotonic contraction within the above-men-tioned range in torque and velocity. (7) Firing rates of single MUs increased with the increase in load-torque and flexion velocity.

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In dental research, occlusal force, masticatory load, tension of soft tissue and condition of the dental arch have been measured. It has not been possible to determine accurately the loads on the teeth and consequently on the periodontal structure. The purpose of this study was to develop a new force sensor, employing piezo plastic film. The sensor must be small, light and thin, and several designs were made. The film was used to measure the following forces: 1) tapping force; 2) behavior of the impact force applied to the teeth to evaluate their supporting structure; and 3) interproximal force transmitted in the dental arch. The force sensor was designed to be very small and light weight to attach easily to the teeth, and was made so thin that it could be inserted into the interproximal spaces. Because the stiffness of the piezo plastic film allows for high mechanical impedance and negligible deformation of the film under load, our sensor is a force-measuring device superior to those presently available. Even though the electrical out impedance of the film is high, it is suitable for the measurement of fluctuating forces. The force sensor needs no source voltage so that it can be used safely on the human body. The improved sensor design will have broad application in dentistry.

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Recently, the results of research on the brain have been looked at with fresh interest. The major reason for this is that the reference techniques for the brain have made remarkable progress. Besides, this interest has been stirred up by the fact that the abilities of future intelligent robots may approach those of the human brain. We are concerned primarily with the question of what sort of space is prepared for writing motor imagery in the brain. Thus, this paper infers the motor imagery space on the basis of motion analysis of writing. In this paper, the relation of the upper limb posture and the pen stroke in writing is analyzed. The measurement of the upper limb posture in the writing motion is carried out using an exoskeletal-type goniometer. This goniometer has ten degrees of freedom to cope with the redundancy of the natural upper limb motion. The writing goniograms indicate that the bladebone rotation is negligible and that elbow extension and flexion and shoulder rotation specify the rough letter forms. The pen stroke is shown by velocity and acceleration in the direction of the writing progression or the writing force. The writing force is obtained by taking the gauge of the strain of a phosphor bronze plate pushed up with ball-point penholder fitted into a stylus pen. According to our observation, variations of writing force are related to the motions of wrist dorsal flexion and palmar flexion, and also shoulder adduction and abduction. Further, as the result of principal component analysis, factors peculiar to the motor imagery space are extracted from the combinations of the writing goniograms. Hence, we suppose that the motor imagery space in the writing will be formed in consideration of the writing sphere relative to the shoulder position.

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In order to characterize human gait, a complex and individually different phenomenon, specific measured variables such as distance and temporal factors of foot-floor contact are used, since it is a typical stochastic phenomenon. Using data input devices for computer graphics such as a tablet and a digitizer, we developed a wirelatticed twelve-meter-long walkway and micro-computer software for obtaining position foot stamp data by high-speed sweeping. Previously, we reported the construction of a prototype walkway and the experimental measurement results. In this report, we completed improvement of the system and again collected measuring data. The advantages of the improved system compared to the proto-system are: (a) exchange of micro-computer for a more advanced one; (b) improved switching sensitivity; (c) compact and refined signal sweeping rate electric circuit assemblies; and (d) adjustable Using this system, we collected a number of data concerning normal gait, and introduced general and valid results based upon the statistics. Further, we assessed the right and left symmetricity, the variations of gait parameters and the difference in gait between males and famales.

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A micro-computer-based real time measurement system of 3-D motion has been developed using multiple position sensing detector cameras. The multiple-camera system has been introduced so as to reduce the probability that a measured part is hidden by some other part of the object from either one of a stereo-pair of cameras to be used to calculate 3-D position. The system monitors each movement of up to 16 LEDs attached to various places of a moving or a deforming object, which are turned on in a sequential manner. Multiple cameras, up to 8, surround a measured object so that light flux of any one of LEDs on the object can be received simultaneously by at least two of the cameras. Each camera sends its position output and incident light intensity output of an LED to an I/O processor (8-bit micro-computer PC 8001). The I/O processor compares light intensity outputs among all of the cameras and selects two of the cameras as a stereo-pair for 3-D position calculation which give the strongest output among them. A 16-bit micro-processor (8086) and a co-processor (8087, high-speed arithmetic unit) receive these two position outputs and calculate an instantaneous 3-D position of an LED within 3 msec. The system employs a novel method of determining the orientation and position of each camera relative to the objective space. First, by minitoring LED movement along lines parallel to the X-, Y- and Z-axes of the space, an 8-bit micro-computer (PC 8001) determines rotation matrix of a camera using directions of given LED movements and equations of image lines of them. Second, by displaying an LED at various known positions in the space, the micro-computer calculates the 3-D position of each camera center using the (X, Y, Z) coordinate of the LED and corresponding camera output. This method saves the trouble of complex presettings of cameras, which most previous systems were subject to, to take some particular postures and positions, and also excludes possible measurement errors, which otherwise could be introduced by unavoidable missettings of cameras. Other techniques are employed to improve measurement accuracy and to reduce noise, including real time correction of spatial distortion of position outputs of the PSD cameras. Average measurement error and minimum detectable displacement (noise) have been proved less than 0.5mm over central cubic region (40×40×40cm^3) and less than 1.0mm over peripheral region (60×60×60cm^3) of the measurement space.

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Using surface electrodes, we have developed and tested clinically FES systems for lower and upper limbs of hemiplegic patients and for upper limbs of quadriplegic patients. Furthermore, we have studied fatigue of muscle contraction caused by FES and intermittent sinusoidal high frequency stimulation. We have developed a peroneal stimulator for hemiplegic patients. Now, we are waiting approval of the Ministry of Welfare before putting it on the market in Japan. Clinical factors of hemiplegia relating to the peroneal stimulator were analyzed in 80 patients. It was found that hemiplegic patients who were slightly spastic and above stage IV of lower limb functional level (Brunnstrom) were good candidates for using the FES. According to our experience. FES was very suitable for the Japanese life style. We also developed a one-channel stimulator for upper limbs of hemiplegic patients. The stimulator was suitable for patients who have hypertonus of finger flexors. We have developed a two-channel stimulator for C_5-level quadriplegic patients. Finger flexors and extensors of only one hand are stimulated through two pairs of surface electrodes by this stimulator. The stimulator is controlled by a toggle switch which is manipulated by the other hand. Although the method of control is on/off in this system, strength of stimulation is increased gradually at the start of so that finger movement is gradual. In order to get active prehension and release by two-channel stimulation, a splint which stabilizes the wrist and thumb in the functional position was used. Furthermore, four fingers, the index finger to small finger, were held together by the finger support. In performance tests with three patients, it has been proven that quadriplegic patients are able to restore grasping by using this stimulator. We have measured muscle fatigue during FES and the period which is required for its cessation. In case of 60-second stimulation, 60-second off time was required for 90% restoration of grasping force. We have studied intermittent sinusoidal high frequency stimulation both in order to increase grasping force and to control pain. It was found that the grasping force by intermittent sinusoidal high-frequency stimulation (5.7kgf) is larger than grasping force by low-frequency stimulation (3.2kgf). However, patients who were stimulated by intermittent sinusoidal high frequency complained of more numbness than those stimulated by low-frequency stimulation.

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The conventional wheelchair sling provides little or no support for the spine of patients with myopathy or neurogenic muscular weakness. As the spinal muscles become weaker scoliosis may develop with associated deformity, pain and restriction of cardiorespiratory function. The purpose of this study is to resolve seating problems for children with myopathy or neurogenic musclar weakness. This paper describes a measurement system of pressure distribution in the buttock region that is used with a pressure senser and mini-computer, and describes new ideas for electric wheelchairs using a Magic Moulded Seat and recliner-type wheelchair. A study of 34 Duchenne Muscular Dystrophy (DMD) patients analyzing pressure distributions was conducted. The following results were observed: (1) Scoliotic-type DMD patients exhibit a single supporing pattern of pressure distribution while in the seated position. (2) When compared to healthy subjects of the same age, DMD patients, who have difficulties with sitting balance and posture, exhibit unequal weight pressure. This imbalance results in muscular pain and reduced contact on the gluteus maximus. (3) Severe scoliotic-type DMD patients are unable to tolerate this pressure area with lateral flexion of the trunk. These results led us to attempt to develop a method to provide comfortable seating posture using a Magic Moulded Seat and an reclining-type electric wheelchair (Lowver R) that would help control spinal deformity and reduce pain in DMD patients.

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A portable electronic device has been developed for controlling the limb load exerted by a patient in a partial-weight-bearing walking exercise. The device consists of three units: 1) a capacitive load transducer and a pre-amplifier that detect limb load; 2) a main electronic unit which converts the output of the pre-amplifier into avoltage signal and generates feedback tones; and 3) a meter used to adjust the voltage gain and threshold levels. The capacitive transducer is shaped like an insole and can be attached to the sole of the shoe from outside by elastic bands and Velcro straps. The transducer is divided into a front unit and a rear unit; thus the load exerted on the front part of the foot and the rear part of the foot can be separately measured. The transducer is thin (3.5mm), light (130g) and flexible, so it does not hinder the natural gait pattern. The main electronic unit converts the change in capacitance of the front and rear units into voltage signals and adds them to generate a voltage signal corresponding to the total load exerted on the foot. The main electronic unit measures 160×110×35mm and weighs about 430g and is fastened at the waist of the patient. The device has two basic operating modes: load-amplitude mode and stance-duration mode. In the load-amplitude mode, the load is compared with two presettable thresholds and two audible feedback tones are generated. A low-frequency tone is emitted when the load falls in the desired range, i.e., between the lower and upper thresholds, and a high-frequency tone is activated when the load exceeds the upper threshold. Thus, the patient is asked to walk so that he/she hears only the low tone in each step of the affected limb. In the stance-duration mode, the load is compared with the lower threshold, and the low frequency tone is generated if the load is maintained above this threshold for a period longer than a presettable stance duration time. This mode is used primarily for the purpose of encouraging the patient to exert the load on the affected limb for a longer period. In both modes, the load compared with the threshold(s) is the total load in usual application, but the load exerted only on the front foot or the rear foot may be used if so required. The feedback tone is transmitted to the patient via an earphone, and is simultaneously transmitted via commercial FM frequency so that an accompaning PT can monitor the tone by FM radio. To evaluate the effectiveness of the feedback tones in controlling the limb load in the loadamplitude mode, an experiment was made. Forty-two normal subjects and 17 patients with lower limb fracture were asked to walk at prescribed load ranges. These load ranges were 15-25kgf, 25-35kgf and 35-45kgf in normal subjects. In the case of patients, the upper threshold was set at the maximum load level allowed at the time of the experiment and the lower threshold was set 5 to 10kgf below this level. Each subject walked on a 15-m straight level floor with two crutches, and 50 steps were selected for data analysis. When the feedback tones were not trasmitted to the subjects, the peak load fell into the prescribed load range in less than 50% of the steps in normal subjects, and the peak load exceeded the upper threshold in more than 50% of the steps in the patients. When the feedback tones were transmitted, the peak load was maintained in the prescribed range in more than 80% of the steps both in the normal subjects and patients. The variation of the peak load decreased in the majority of the subjects when the feedback tones were heard. These results demonstrate that the feedback tones are very effective in controlling the limb load and to reduce the mental tension of patients during exercise.

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In the management of various diseases, the condition of a patient can be known only from the various inspective or retrospective diagnoses at the hospital, and the change in the condition of a patient in daily life cannot be known exactly. From this point of view a portable biological information recording and analyzing system, MICRO (Medical Information Collection RObot) is developed here, which can record and analyze many kinds of biological signals in the patient's daily life, not only at hospital but also at home. The MICRO is a kind of a pocket-sized battery driven micro-computer system, and by carrying this, many kinds of medical information about the condition of a patient in his daily life can be acquired. The size or function of this small system should be changed according to its surrounding enviroment, purpose of recording, the object of measurement or the patient's condition. In practice two types of MICRO have been developed. One is a kind of event counter and is equipped with four button switches to record the occurrence time of objective events, and a mercury switch to record the patient's body swaying. The output of the mercury switch is affected by the patient's motion and is thought to indicate well the condition of a disease. This type of MICRO is applied to record pain fluctuation in the daily life of the rheumatoid arthritis patients. As a result, the pain fluctuation in one day is proved to be rather coincident with the condition of the patient. The other type is a kind of data recorder with an instrumentation amplifier and A/D converter, and it can record many analog types of biological signals, like electrocardiograms or the eletromyograms. A long-term monitoring of the electromyograms of paralyzed patients is one clinical application of this type. The other clinical application is a measurement of the pressure distribution under the foot. A new method has been needed to measure in more natural states, like in the wearing of shoes or where the electric wave does not arrive if using a telemetry system. The results show that the MICRO can stably measure the pressure under the foot in such natural states.

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In artificial joints, prosthesis loosening is influenced by its design and fixation technique with the bone. There are many designs of total knee prosthesis, including the hinged and nonhinged condylar type, in use today. In many recent clinical reports, sinking and loosening have been cited as a significant complication. For the purpose of making clear the relation between the loosening and the prosthesis design, a machine simulating the knee joint was manufactured and the relative deflections on the surface of the bone and between the component and the bone were measured by means of the strain gauge method utilizing the dynamic loading test. For the tests, GUEPAR prosthesis, Kinematic Rotating Hinge prosthesis, Total Condylar prosthesis and KOM Ceramic prosthesis were prepared. Fourteen different tibial components were also prepared including one compartmental, two anteriorly joined, eleven one-piece components with one, two, or three fixation pegs, all-plastic components or those with metal trays or with ceramic trays, for purpose of comparision. These prosthesis were fixed in femurs and tibia of cadaver bones with cementing. Strain gauges were glued to the surface of the around knee prosthesis, using cyanoacrylate instant cement. Maximum load was 100kg. In the GUEPAR prosthesis representative of the hinged type, the deflection was much larger at some distance from the knee joint, especially around the tip of the femoral stem, than in the periphery. In the Kinematic Rotating Hinge prosthesis, the hinged type admitted rotational movement, and the load was transmitted to the posterior cortical bone of the femur and tibia and compressive deflection occurred on these parts. The deflections were decreased around the tip of the stem. In the femoral component of the non-hinged type, KOM Ceramic prosthesis and Total Condylar prosthesis, the deflection around the periphery of the joint was not abnormally larger than the physiological state. In the tibial component, on the other hand, the compartmental component and anteriorly joined and one-piece components with short pegs deflected the most on the periphery of the anterior of tibia where the subchondral bones and trabeculate were weak and the cortical bones were thin. The least deflections occurred with the components with one or three strong pegs transmitting the load to the thick cortical bones. In fixing the tibial component, if it is designed to be loaded on the rigid cortical bone and is fixed so as to be supported by the rigid subchondral bone and cancellous bone of the plateau as well as by the rigid cortical bone on the medial and lateral sides or posterior slant surface and then loads are transmitted, it is considered that abnormal stress concentration can be decreased. The metal tray and ceramic tray prevent the deformation of the plastics and the stress concentration on the bone and cement.

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A socket of the total hip prosthesis is 1) fixed with bone cement or 2) placed without bone cement. The stability of both methods was investigated under severe loading conditions. A two-dimensional finite element model was used and its cross section was cited from CARTER, VASUS and HARRIS. Sockets were set by four methods. In Cases 1 and 2, bone cement was used for the installation and fixation of sockets, although the two differed from each other in the mode of anchoring. The anchoring of Case 2 is based on the theory that the inner wall of the cortical bone is expected to be a supporting area, in Cases 3 and 4, bone cement was not used. Acetabular dysplasia was absent in Case 3 and present in Case 4. Boundary non-linear elements were considered at the interface between the bone and bone cement in Cases 1 and 2, and at the interface between the bone and a screw-socket in Cases 3 and 4. It was assumed that HDP and bone cement as well as HDP and a screw-socket were united. The program used in the analysis was MSC/NASTRAN. The load employed was 10kg in all cases, and it was considered that as a three-dimensional effect, a socket would be given rotatinal force to some extent. Therefore, Moment M=2.55kg.mm was made to distribute on the inside surface of HDP. These loading patterns are severe conditions from the clinical point of view. A model for analysis was fixed with its top and bottom ends. Cases 1 and 2 present considerable deviated distribution of contact area pressure. On the back of the cortical bone, no contact pressure was detected. In Case 3 and 4, the interface between the bone and implant was again separated. This displacement is likely to occur in clinical cases. The amount of displacement in Cases 1 and 2 was considerably larger than that in Cases 3 and 4. In Cases 3 and 4, support by the cortical bones on the back resulted in a smaller amount of displacement. In the case of restraining both sides of the cortical bone, there is considerable estimation of rigidity on within-area bending deformation of the cortical bone. Both sides of the cortical bone were thus restrained. In all the cases including Case 1D through Case 4D, distribution of the contact area presure was uniform. Subsequently, the displacement was small.

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The ISNY (flexible above-knee) socket has been introduced recently by facilities in Iceland, Sweden and New York University. The socket consists of two parts. One part is a strong strut horizontally around the ischial sheet, and vertically along the medial portion. The other is a flexible (but not elastic) socket made of a low density polyethylene sheet. Many amputees who were fitted with the socket report significant improvement in prosthetic comfort. In this study, we have attempted to evaluate the socket biomechanically. Using a micrometer, we measured thickness in many different portions of the socket. The thickness was 1.5±0.4mm on the average. Using linear motion transducers, we measured the amount of socket wall movement during walking. The amount of movement during walking was not so large, about 2mm in most portions and about 5mm at maximum. The socket shape change seems to correspond more to the force by the stump lever arm than to muscle contraction. Using strain-gauge pressure sensors, we measured stump-socket pressure both of the ISNY socket and the conventional hard socket during walking. The result indicated that the stumpsocket pressure was almost same in these sockets. Using X-ray examination, we measured adduction of the femur both with the flexible socket and with the conventional hard socket in standing. We found there was no difference between the ISNY socket and the conventional hard socket concerning femur adduction. At the present stage, we think the ISNY socket is biomechanically similar to the suction socket with a soft liner.

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A pneumatic swing-phase control cylinder has been used to improve the gait with an A/K prosthesis. The characteristics of the swingphase control devices are normally fixed during walking. The gait pattern is acceptable only when the gait matches those devices. It has been proved that it is possible to automatically adjust the damping characteristics of a pneumatic control cylinder to a wide range of walking modes with the help of a micro-processor. This paper first summarizes the mathematical modeling of the movement of an A/K prosthesis incorporating a pneumatic swing-phase control cylinder. Through the analysis of this model, an optimal control problem is equated to simulate the movement of knee flexion of a normal gait during swing phase for wide ranges of walking modes. A prosthetic knee unit has been developed to prove the optimal control. All of the controlling components including batteries are contained in the unit. Walking speed is measured by time during the stance phase of a prosthesis. A new body weight switch has been developed to sense the time and is used as input to a controller. With the introduction of a C-MOS onechip micro-processor and a refined valve mechanism of a cylinder, it became possible to operate the control circuit for about 16 hours with a 6V/225mAh small rechargeable battery and the valve actuator is workable for 3 continuous hours with a 12V/225mAh battery. The valve actuator needs energy only when it is actuated; this means that an amputee is able to walk more than 10km when a battery is fully charged. This corresponds to a whole day of walking in normal conditions. The prosthesis tested is about 300g heavier than conventional prostheses. The weight is within the range of ordinary ones. It is concluded that the authers could propose an A/K prosthesis which is functionally superior in practical use.

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This paper deals with an attempt to develop an above-knee prosthesis which allows amputees smooth stair descending and level walking at a voluntary walking pace. First, the dynamic analysis of normal persons' level walking and stair descent/ascent were carried out to obtain general prospects for the design and the control of an A/K prosthesis. The summary of the analyses is as follows. (1) The active planter-flexion moment (more than 100Nm) must be effected at an ankle joint on a stance phase during stair-ascending. (2) The passive extension moment (max 80Nm) must be effected at a knee joint on a stance phase during stair descending. (3) A little active extension moment is necessary at an ankle joint on a swing phase for rapid walking to walk on a flat surface and also to ascend stairs. (4) A passive flexion moment must be effected at an ankle joint through a swing phase during stair descending; however a little extension moment (about 3Nm) is necessary at termination of a swing phase to sustain some extension angle. One hydraulic actuation system was then proposed on the basis of the analytical results, which allows amputees to descend stairs smoothly as well as to walk on a flat surface with no external power source. The proposed system was assembled into the A/K prosthesis WLP-7. Amputees wearing WLP-7 can walk on a flat surface at a voluntary walking pace and also can descend stairs as well as normal persons after only half an hour of training.

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A system is developed to measure various functions of the artificial leg continuously for long periods under any walking conditions. The system is composed of two parts. One is a measuring subsystem of portable size, movable anywhere with the subject, and the other is a data processing subsystem located in the laboratory. The measuring subsystem is constructed from a pylon load cell installed in the shank part of an artificial leg to measure six quantity forces, and flexible electrogoniometers attached on each side of bilateral hip, knee and ankle joints. This goniometer is made of electro-conductive silicone rubber mounted on an elastic rubber beam which is self-aligning, very light weight and compact. Very large time series data obtained by the measuring subsystem is processed efficiently in a relatively short time by the data processing subsystem constructed from the interactive graphic terminal connected to the minicomputer. With this monitoring system, the dynamic alignment of below-knee prostheses was measured. Some of the quantitative relations between the displacement of the foot to anteriorposterior or medial-lateral directions in the horizontal plane, and patterns of load on each part of the prosthesis and/or angles of both side joints were examined. Minute information about the behavior of each part of the lower limbs has been attained, which could not be obtained by previous studies measuring the locus of the gravity center or other macro parameters. This knowledge gives a concrete base for the best dynamic alignment of an artificial leg for individual amputees.

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The object of our studies is to automatically measure the residual hand of an amputee and to systematically produce a prosthetic hand. It is also our object to produce a micro-computer-based measuring system which can quickly process reductions, magnifications, changes, additions and corrections, and to produce a manufacturing system which can effectively utilize numerically controlled machines. We have measured the hands of about 30 normal persons and those of 6 amputees in a manner which enables us to model a prosthetic hand comparable to a normal hand. The outcome of those measurements has been to produce a prosthetic hand which is useful in the rehabilitation field. The prosthetic hand has been designed to have adaptive functions and to be a functional hand, with various grip models, including that of "shaking hands," for example. Using a CAD system, we have designed a cosmetic cover and inner model in which MP, PIP and DIP joints move separately. As results, (1) The functional cosmetic hand was designed by CAD system. (2) Up to now, it has been impossible to store all the numerical data of the residual hand. (3) Commonly, functional hands were designed from a simple, standardized length measurements. (4) Individually matched manufacture has become possible, because the shape of the residual hand is reversed in the micro-computer. (5) Data processing such as magnifications, reductions and eliminations, which required a great deal of time previously, has become much easier. (6) In addition to the utilization of the system in rehabilitation, it is possible to use various transformations to obtain an estimation of the shape of the hand in different positions (for example, cosmetic aids for hands of patients with rheumatism.)

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The final goals of prosthesis research are to develop artificial limbs which are naturally controlled by the amputees' motor intents and are functionally responsive like natural limbs. However, most prostheses in present use are still far from the goals in spite of recent advanced technologies for robot manipulators. In human prosthesis systems, amputees' motor intents must be transmitted through the remaining functions. Therefore, information transmission is largely restricted and the control properties of human prosthesis systems are inferior to these of regular man-machine systems. Improvement of the control properties requires development of more cybernetic interface between an amputee and an artificial limb. In this paper, the force and position controls of human prosthesis systems are analyzed from the view point of their dynamic property. First, to analyze the force control, tracking tests controlled by myoelectric signals were performed. Open loop describing functions show good characteristics and it was shown that one of the most important problems in the force control of human prosthesis systems is the influence of sensory force feedback to control characteristics. A human prosthesis interface with bilinear structure is proposed. The bilinear structure makes it possible to control the mechanical impedance about the joint. The test results of tracking performance demonstrate that the position control could be largely improved by adding the bilinear structure to the interfaces in human prosthesis systems.

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Legged locomotion over irregular terrain is composed of body propelling motion and terrain adapting motion. Although conventional walking machines with three active degrees of freedom (d.o.f) for each leg can adapt their feet on irregular ground using flexible leg freedom, such machines generally require a tremendously complex control scheme for the body propelling motion, because cooperational control of leg freedoms in stance is required for a system with several closed kinematic chains between the body and the ground. To cope with this problem, a walking machine with decoupled freedoms, described in this paper, is based on the idea that body propelling motion is realized by only one degree of freedom and can be perfectly decoupled from the freedoms for terrain adaptability. In this type walking machine, the control system is perfectly released from the control of closed kinematic chains. Therefore it can be expected that the control algorithm will become much easier than that of conventional walking machines having three active d.o.f. per each leg. First, the authors discuss such walking machines and make clear the quadruped walking model with minimum active d.o.f. through basic considerations of freedoms of walking machines. Next, according to observations of animal locomotion, a hexapod walking machine (MELWALK) with decoupled freedoms using an approximate straight line mechanism is developed in order to realize faster and simpler walking machines than the quadruped one. As the foot pattern of this walking machine is limited to only one pattern, other kinds of freedoms are established to implement a body direction changing motion and a terrain adapting motion. Rotational freedom other than propulsion is added to implement the body direction changing motion, and extension and contraction freedom to the legs are also added to implement the terrain adapting motion. Although more than two active d.o.f. for each leg are desirable for terrain adaptability, the proposed walking machine has only one active d.o.f. for simplicity. Experiments are carried out to certify the body propelling motion, terrain adapting motion and body direction changing motion. It can be recognized from the trajectory of LED that the body proceeds along an approximate straight line close to an exact one. Body direction changing motion is implemented with relatively high speed. Furthermore in order to check energetic efficiency, the power consumed by DC motor is also measured using MELWALK MARK-I. Several features of the proposed hexapod walking machine are revealed through these experiments.

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