近年,高齢者の人口が急速に増加している.高齢者は,一般に加齢に伴い筋力が低下するため,自力での歩行が可能であっても疲労しやすい.また,本人は普段通りに歩いているつもりでも,疲労するにしたがって歩行時の足の位置,角度などが変化していくため,わずかな段差であってもつまずきやすくなる.このような歩行機能低下時の転倒事故により,自信喪失および介護者を必要とする状態に陥るケースが多い.そこで本研究では,高齢者およびリハビリ患者の自立生活の支援を目指すため,足には固定せずに,膝関節や股関節だけでなく,足関節までを含めた下肢全体の歩行支援をする動的歩行補助機を開発した.18年度の時点では,直線方向の歩行のみ補助可能であったが,各種センサを活用しコンピュータの自立化を図ることで,様々な環境での歩行を可能とした,19年度における開発成果を以下に記す.1.足首のひねりをリンクの変形から検知し,左右の歩幅を調整することで方向転換を可能とした.2.本装置が平行リンクを用いた構造であることから,腰部背面に傾斜センサを取り付け,装着者の立っている地面の角度を検出し,装置の軌道を補正することで,傾斜面に応じた歩行が可能となった.3.健常者の階段昇降時の関節角度変化を計測し,装置装着者に応じた制御軌道を生成する手法を提案し,かつ,非接触距離センサを用いて段差との距離を計測することで軌道を補正し,腰きを防止した.4.SH4およびリチウムイオンバッテリーを装置に搭載し,自立化したことにより,行動範囲の制約を受けず,自由に移動可能となった.また,約1時間の連続稼動による屋外歩行を確認した

上肢および下肢を補助可能な全身動作補助機開発した.本装置は歩行やADLを補助可能とする.本装置を用いた歩行時の脳活動を計測し,ニューロリハビリテーションの効果を検討した.その結果,トレッドミル上では装置に慣れてくると脳活動が低下するため,腕振りが重要であり,トレッドミル上よりも移動しながら訓練をすると脳活動が活性化することを確認した

In this study, we proposed a method which could be used for mapping people's emotion state on the two-dimensional arousal-valence model of effect. The final target of our research is to apply this kind of emotional recognition system to robots or some assistant apparatus which service activities of daily living (ADL). Since in our previous studies, we have finished the work of recognizing people's emotion state on the dimension of arousal by evaluating subjects' heartbeat and LF/HF, which is calculated from the frequency domain analysis of HRV, as the second step's work, we focused on how to recognize people's emotion state on valence dimension. To be specific, we used some kinds of normative affective stimuluses to elicit subjects' emotional change, then collected multiple physiological data during this emotional stimulation process. Finally, as for data analyzing, we didn't use the supervised learning method, like SVM, but made a new attempt to apply the unsupervised clustering method to sample data, dividing the data set into several natural clusters by analyzing the physiological features we abstracted. The calculated results of our experiment have verified the feasibility of mapping human's emotion state on the two-dimensional arousal-valence model of effect at a quadrant level.

<p>We developed small type of a standing up device for the elderly. We have developed standing up devices; caster walker type and bed wheel chair type. They assist standing up motion, backed on following two conditions. 1) the trajectory of center of gravity of the user is round shape, 2) the trajectory of the hip joint of the user while standing up is straight line. These conditions were found from the data of able bodied elderly people, and the feature of their standing up conditions is to lean forward the upper body. By using these devices, the load of the knee joint decrease, and the user can learn how to stand up easily. However, these devices are bulky and usable scenes are limited. Then we developed small type, which can be used on various chairs. This type assists from sitting posture to the middle phase while standing up. The mechanism is constituted with links and a gas spring, instead of a motor. It is light weight, low cost, and small to be able to attach to the back of a chair. From the calculation, by using this new type, the output torques of the knee and ankle joints decreased.</p>

<p>A walking assistance apparatus using a torque limiter was developed. We used the servo motor for hobby, it is relatively small, light weight, and included not only a motor and transmission gear, but also a driver and encoder. At first, we controlled the device using angle control method, according to the walking phase along to the mean data of able bodied people while walking. However, when the user stops walking suddenly or walk on outdoor various roads, the final gear was broken frequently. Because the gear was designed to break easily, to defend the motor from the inverse inputting overload torque. Then we developed a torque limiter mechanism in the final gear. This is a traction drive sandwiched a soft material plate between two circular disk. We carried out the experiment to measure the limit torques of eight kinds of the rubber material. In this paper, the results of the experiment were shown.</p>

<p>Wear on tooth surface of gears occurs while gear pair transmits a power and a rotation. The progression of the wear gradually degrade the performance for the change in the tooth profile. Especially, the edge contact provides a large wear to the tooth surface. A tooth profile modification is widely used to prevent the edge contact. However, there is few researches about the effect of tooth profile modification to the surface wear. In this study, we investigated the effect of tooth profile modification on the tooth wear of involute spur gear in the cyclic wear test with two types of gears. Furthermore, we developed a computer program to predict the amount of the wear on the tooth surface considering the edge contact for the spur gear. The method is based on two types of wear equations. One is Soda's theory under lubricated condition, and the other is derived from the ploughing wear model. We compered the calculated result with experimental data, and discussed the effect of the tooth profile modification on the tooth wear.</p>

<p>Recently, value creation from view point of service has been widespread. A service process is regarded as a kind of interaction between service providers and receivers. Sharing and managing such the knowledge on human Kansei are of growing significance to providing product's values focused on customers. However, any sufficiently-advanced technologies that realize such knowledge sharing and management have been established. One typical approach is to clarify and systematize concepts as an ontology which is a basis to describe knowledge. In the current study, we discuss a method to develop an ontology describing knowledge on human Kansei and introduce several existing ontologies. The ontology will serve as a useful reference to develop value recognition map and be of assistance to designers.</p>

<p>Recently, improvement of design capability is one of important issues in industry However, it's really difficult to share knowledge of design possessed by experts with novices, because the knowledge exists depending on their skill and degree of prociency. Thus the current study aims to excavate the experts' Knowledge. We then described design objects related to action to design electronic components.</p>

<p>Various walking assistance devices which promote rehabilitation and exercise for elderly have been developed. However, these devices can't support walking for exercise, because many elderly feels fatigue and bored in assisted walking. Therefore, the aim of our current study is to assist not only physically but also mentally elderly walkers to keep up their motivation. Concretely, we propose a walking promotion method that walkers listen to the beat sound adjusted according to their emotions with the ankle support assistance device. In order to confirm the effectiveness of the method, we conducted two experiments. The first experiment has four conditions where walkers have the device assist or not and the beat sound assist or not. As a result, the gait was improved with the device and sound assist where target cadences were adjusted according to their walking cycle. The second experiment has two conditions where walkers assisted sound adjusted according to their emotions or not. As a result, awakening levels perceived by the walkers remarked higher than ones in usual walking. These results showed the effectiveness of the method and possibility of the control of the emotion while walking.</p>

We developed a walking assistance apparatus which can be used for neuro-rehabilitation of patients. This apparatus assists only the ankle joints of the equipped person and he/she can raise his/her leg by using the stretch reflex to bi-articular muscle. To confirm the effectiveness of the apparatus, we carried out the experiment for the patients of walking with wearing the apparatus, and the angle variation of the ankle was measured. From the results, by using this apparatus, the dorsiflexion and plantarflexion of the ankle joint of the equipped person can increase while walking. Furthermore, to grasp the lifetime limit of the apparatus, we developed the fatigue test apparatus for the power transmission device of the walking assistance apparatus: from the motor to the worm-helical gearbox through the flexible shaft. This apparatus supplies the power with the motor which is the same as the motor which is used in the walking apparatus. As a result, we could define the limit to replace of the flexible shaft according to the condition of the user.

We developed a motion assistance apparatus which can be used for neuro-rehabilitation of patients and for the promotion of exercise for the elderly. This apparatus assists only the ankle joints of the equipped person according to the posture of him/her while walking, getting up, sitting, and standing. To confirm the effectiveness of the apparatus, we carried out the experiment of walking with wearing the apparatus, and the angle variation of the ankle was measured. From the results, by using this apparatus, the dorsiflexion and plantarflexion of the ankle joint of the equipped person can increase while walking. Therefore, this apparatus can prevent stumbling and promote walking and various motions.

Recently, view point of service has been widespread. In learning domains, service providers have been required to adopt it and to provide values co-created by teachers and learners. The current study aims conceptualization of learners states extracted from utterance contents agreed by a teacher (mentor) and a leaner along with conversation analysis in the previous study. As a result, we proposed ontological descriptions which clarify ASIS/TOBE states perceived by teachers and learners.

Recently, view point of service has been widespread. In learning domains, service providers have been required to adopt it and to provide values co-created by teachers and learners. The value co-creation takes place in joint sphere where providers and customers make interaction, and the value is subjectively perceived by receivers (learners in learning service). That is, a mental state of leaner is one of possible value in the co-creation. The current study aims to develop a conceptual framework which describes mental states of learners for specifying values in the co-creation. As a result, we proposed ontological descriptions of learning event which consists of a teacher, a learner, learning materials, and a learning action by the learner. In concrete terms, we proposed ontological descriptions for receiver states in a learning activity, on the basis of a conceptual model of value co-creation. The ontological descriptions are useful for sharing knowledge on values perceived by learners to design learning services.

<p>高等教育においては，教育サービスの提供者と受給者が目標とする学習成果についての合意形成を行うことで，高い利用価値を共創的に実現することが期待される．本研究では，合意形成の過程を可視化するために，合意された話題の意味内容の概念化を試みる．具体的には，メンターと学習者のカウンセリング事例を取り上げ，サービス提供者，受給者，コンテンツ・チャネルとして発話内容を位置づける．</p>

Flexible shaft is bent elasticically, and then it is possible to change the direction of power transmission freely. It consists of some layers of wires those are rolled alternately around the core. Due to the construction, twisting properties are strongly depending on the direction in which the wires of external layer rolled. In this study, we measure the twisting properties of flexible shafts for both directions, one is the direction of the external layer rolled and one is opposite. Experimental results show the twisting property is independent of the length of the shaft and bending-radius. The second rigidities are completely different depending on the twisting direction. In the case of shafts those have use history, the second rigidity is got smaller and width of the first rigidity is got larger.

A walking assistance device using a flexible shaft was developed. A combination of the flexible shaft with a worm gear was successfully adopted on this device to modify its appearance simple and suitable size. This device is also controlled with a hybrid-control system both torque, ankle joint range, and knee joint. In this system, the tensional spring constant of the flexible shaft is taken into account to the control power and the rotating motor of joint angle. To expand the area of where an equipped parson can walk with the device, a self-contained system that operated with SH-4 microcomputer and actuators, which consisted of motors and gears, were put in the small backpack, and Lithium-ion battery was utilized. Therefore, the equipped parson and patient can freely walk both in and out of doors environment.

A new apparatus to assist an elderly person to stand up, as well as leaning forward the upper body, has been developed. The mechanism of the apparatus enables to shift the person's center of gravity along an adequate trajectory during standing up process, so as not to cause strain for each joint of the elderly's leg. The apparatus also assists a person to alter from standing or sitting posture to lying posture. Although the mechanism has multiple links and joints, only one actuator is required to transform the apparatus between aforementioned three postures. The length of each link of the mechanism has been determined from their effect on the backrest angle when each link length is changed. Each torque of hip and knee joint of the person while standing up was calculated, and effectiveness of the apparatus has been confirmed.

We developed a walking assist apparatus, which machine used a spatial parallel link mechanism for the elderly and rehabilitants. Without making special constraints on person's legs the proposed apparatus can assist whole legs of a person including soles. The apparatus was equipped a inclination sensor and an ultrasonic sensor, then the angle of the slope and the size of stairs are measured to generate the control signal. To examine the effectiveness of the proposed apparatus, the muscle fatigue while walking with wearing the apparatus was evaluated for one hour by MPF of the measured data of electromyography. As a result, the MPF wearing the apparatus was on maintenance tendency. Moreover, the muscle activity in walking up the stairs was evaluated by IEMG Therefore, the effectiveness of the apparatus could be confirmed. The apparatus used with patient lifter to examine the use for neurorehabilitation.

A new control system for power assist apparatus for an upper limb was developed. This apparatus can select two control systems. One is the deferment type use a power supply for household wall socket to operation for a long time, and use desktop PC for operating. The another one is Self-Contain type that uses battery for power supply therefore it was assumed that could use it outdoors. However the Self-Contain type was apprehended thermal runaway. Therefore developed device a countermeasures against heat. Third movement what could make support to three dimensional end motion further out analysis the range of movement developed apparatus was added to the apparatus. Some input devices were made to manipulate our apparatus and evaluated from subject's comment.

In this paper a walking assistance device using a flexible shaft was developed. This apparatus assists the walking and standing up motion. A combination of the flexible shaft with a worm gear was successfully adopted on this device to modify its appearance simple and suitable size. This device controlls torque, ankle joint range, and knee joint with a hybrid-control system. In this system, the tensional spring constant of the flexible shaft is taken into account to the control power and the rotating motor of joint angle. To spread the moving area with the device, a self-contained system operated with SH-4 microcomputer and actuators, which consisted of motors and gears, were put in the small backpack.

We are currently developing a Guide-Dog Robot for visually-handicapped person. In our concept, the robot should have a movable platform, human-machine interface and capability of avoiding obstacles. For leading them safely, the robot is required to detect their position correctly. At the same time, it is required to detect a direction that people are walking. In this paper, the algorithm for a human-machine interface to lead the people is proposed. Getting the position data of a person as follower into account would be considered by this algorithm. To realize such an intelligent leading, we propose the new algorithm that a robot detects the center of corridor and foot of the follower simultaneously with a laser range finder (LRF). Also, the prototype robot is verified that it can lead a person successfully and safely.

We developed a power assistance apparatus attached to the upper limb, using differential gears for nursing care, or workers who often lift loads up and down. Two motors behind the shoulder of the equipped person provide motive power to drive shoulder and elbow joints, and the differential gear makes it possible to divide the power between them effectively. Shoulder-joint link mechanism was taken into account the Five degrees of freedom of shoulder blade motion. In order to assist the motion of three degrees of freedom with motors, the actuator for shoulder abduction motion was added. By means of three actuators, this apparatus can be supported the behaviors in daily life; meal, face washing, and makeup, and so on. To grasp the behavior of the arms of the equipped person, pressure sensors were attached under the upper and lower arms. Furthermore, the experiment that the apparatus supported the equipped person's three-dimensional motions included in the behaviors which described above was carried out. As a result, the arms of the equipped person could be moved at will, and supported the behaviors in daily life.

Walking assistance is necessary for elderly and persons who work long hours or do a heavy activity. In order to comply with social requests, a walking assistance apparatus used a spatial parallel link mechanism have been developed. In spite of the apparatus do not have to be fixed on person's legs, the apparatus can assist whole legs of a person including his/her soles. The apparatus equipped a control unit and lithium-ion batteries, and could drive over one hour period. To stabilize the equipped parson's posture for horizontal direction, leaf springs were attached to prevent over-adduction of hip joint. The muscle fatigue while walking with wearing the apparatus for one hour was evaluated by mean power frequency (MPF) using electromyography. As a result, The MPF from the data without wearing the apparatus was decreased, however, the MPF from the data wearing the apparatus was not decreased. Therefore, the effectiveness of the apparatus could be confirmed.

A walking assistance machine using a flexible shaft was developed. A combination of the flexible shaft with a worm gear was successfully adopted on this machine to develop its appearance simple and its size compact. This machine is controlled with a hybrid-control system both torque and angle at ankle and knee joints. In this system, the torsion spring constant of the flexible shaft is taken into account to the control power and the rotating angle of the motor. To expand the area of where an equipped parson can walk with the machine, a self-contained system which controlled with SH-4 microcomputer and actuators which consisted of motors and gears were put in the small backpack, and Lithium-ion battery was utilized. Therefore, the equipped parson can freely walk both in and out of doors.

Although the gearing of crossed helical gears theoretically takes place at a point, the contact point extends over a small ellipse due to elastic deformation under loading. Hence the contact stress between the tooth surfaces is comparatively high. Furthermore, the sliding velocity on the tooth surfaces is higher than for other gears. For above mentioned reasons, crossed helical gears are able to carry only very small loads. To make the most of its good features, it is important to improve the load carrying capacity of crossed helical gears. Two factors, that is, high sliding velocity and high contact stress seem to be important, but here we limit the discussion to the contact stress state. It is worthwhile to examine the subject more closely. Also, it is important to understand the meshing geometry of crossed helical gears, since it forms the theoretical basis of the meshing geometry of other types of gearing. The purpose of this report is exactly to investigate the contact stress states on the tooth surface of crossed helical gears.

Our team has developed a prototype for a walking assistance apparatus for the elderly or rehabilitants; that uses a spatial parallel link mechanism. Its flat steps of our apparatus move in parallel with the ground and can support the whole legs of the person including his/her soles. By using a flexible link which is made from stainless steel and rubber, the apparatus can achieve the twisting motions of the waist and ankle. By using this developed apparatus, the wearing experiment was carried out and the effectiveness of the apparatus was evaluated by the IEMG (Integrated Electromyography). As a result, muscle activity of the RF (the Rectus Femoris muscle) and the TA (the Tibialis Anterior muscle) while wearing the apparatus decreased to sixty percent. Therefore, the muscles on the front of the leg were especially affected by using the apparatus. Furthermore, in order to assist walking indoors, we investigated the assistance methods of walking on a slope or stairs. The apparatus was equipped with a gyro sensor and an ultrasonic sensor; the angle of the slope and the size of stairs could be recognized and the apparatus could be adapted accordingly to the signals from the sensors. As a result of our experiment, the equipped person wearing the apparatus could walk on a slope and stairs at will.

In this paper, a dynamically controlled/powered walking support system was described. Certain requirements must be met when developing a walking support system; it must be light weight and safe. Particularly, in this paper, emphasis is placed on maintaining natural appearance by a simple, small, and lightweight device. To meet the requirements of the walking support system using a simply designed device, development must be conducted considering muscular activity. Muscular activity revealed that the anterior muscles are activated during balancing, and that the tibialis anterior muscle is the most important muscle for assist during walking. Based on these results, a walking support system with dynamic motion assist functions for the ankle and knee joint was successfully developed. The system exhibits suitable functionality and maintains the natural appearance by using flexible shafts for power transmission.

We developed a new diagnostic method by using a laser beam. First, the tooth surface is irradiated by a zonal laser beam from oblique direction, and then an irradiated laser beam line is shifted along the height of the tooth according to gear revolution. The variations of laser reflection between the initial and the present conditions are compared, and it can estimate the condition on the tooth surface. Next, we developed the method to scan the length of the pitting area from the laser reflection data using a computer. To put this method into practical use, the laser sensor was fixed in the gearbox, and the laser reflection from the lubricated gear was measured. These experiments were carried out under the condition of force-feed lubrication. As a result, this method could detect all occurrence of the pitting in the dry condition. To improve the accuracy of the detected length of the damage area, the definition of the value of the first-stage threshold and smoothing of the different data was important. Furthermore, to apply this method to a helical gear, we made the three-dimensional model which located the relation between the helical gear and the laser sensor, and derived the conditional equation that the helical gear can be irradiated by the laser sensor along the tooth trace of the helical gear. By using this equation, we can diagnose the helical gear as well as a spur gear.

In this paper, a new walking assist device on which a flexible shaft is applied. A combination of the flexible shaft with a worm gear is successfully adopted on this walking assist device to develop its appearance simple and its size compact. This walking assist device is actively controlled with a hybrid control system witch control both torque and angle at ankle joint. In this control system, the torsion spring constant of the flexible shaft is took into account to control power and the rotating angle of the motor witch assist over seventy percent power of normal walking. Walking experiments using this machine show the walking assist machine is well fit to walking.

We developed a walking assist machine, which used a spatial parallel link mechanism for the elderly or workers. The flat steps of the assist machine move in parallel with the ground and can support the legs of an equipped person including the soles. The machine can assist the equipped person's motion of walking; turning around during walking and walking on a slope or stairs. Furthermore, in order to support walking more effectively, the machine was improved the power unit, attachment of wearing, and control system. Especially, by using the SH4 board installed ART-Linux, and the lithium-ion battery, we could develop the self-contained machine. Therefore, the equipped person could be free to walk at will.

We developed a power assist machine attached to the upper limb, using differential gears for nurses who care an old person being bed ridden, or workers who often lift loads up and down. Two motors behind the shoulder of the equipped person provide motive power to drive shoulder and elbow joints, and the differential gear makes it possible to divide the power between them effectively. This differential gear system can reduce the backlash of gears. The five degrees of freedom of shoulder blade motion were taken into account with the shoulder-joint link mechanism. Furthermore, to grasp the behavior of the arms of the equipped person, pressure sensors were attached under the upper and lower arms. As a result of the experiment wearing the machine, the arms of equipped person could fluctuate at will.

There are many persons who lost their sight and want to get more flexibility for their activities. But there are very small chances to get new guide dog by about 10%. So we started to serve a guide-dog robot for sight-handicap persons. In the first paper, algorithm of obstacle detection with image processing is proposed. We classified obstacles into three main categories "Pole", "Bar" and "Step" shape, and propose new parallactical difference method included stereo camera on moving vehicle, which detects pole and bar shape obstacles under in-house condition successfully.

We developed a walking assist machine, which machine uses a spatial parallel link mechanism for the elderly or rehabilitants. The flat steps of the assist machine move in parallel with the ground and can support the legs of a person including the soles. The flat steps of the assist machine move in parallel with the ground and can support the legs of a person including the soles. To grasp the walking phase of each leg of the equipped person, pressure sensors were laid under the thenar eminence and the heel of the sole, and the pressure variation at each sensing point was measured. Furthermore, in order to support walking in indoors, we investigated the assist methods of turning around during walking and walking on a slope or stairs. A flexible link was installed in the mechanism for taking into account the twisting motions of the waist and ankle. To grasp the behavior of turning around during walking of the equipped person, pressure sensors were attached outside of the flexible link in both crural parts of the machine. As a result of the experiment wearing the machine, the equipped person could turn around during walking at will.

In this paper, a new walking assist machine on which a flexible shaft is applied. A combination of the flexible shaft with a worm gear is successfully adopted on this walking assist machine to develop its appearance simple and its size compact. This walking assist machine is actively controlled with a hybrid control system witch control both torque and angle at ankle joint. In this control system, the torsion spring constant of the flexible shaft is took into account to control power and the rotating angle of the motor witch assist over 70% power of normal walking. Walking experiments using this machine show the walking assist machine is well fit to walking.

We developed a walking assist machine, which machine uses a spatial parallel link mechanism for the elderly or rehabilitants. The flat steps of the assist machine move in parallel with the ground and can support the legs of a person including the soles. Furthermore, in order to support walking in indoors, we investigated the assist methods of turning around during walking and walking on a slope or stairs. The machine was equipped a gyro sensor and an ultrasonic sensor, the angle of the slope and the size of stairs can be recognized and the machine could control according to the signal of the sensors. As a result of the experiment, the equipped person could turn around during walking and walk in a slope or stairs at will. The subject assisted by the machine was able to walk on a slope up to the angle of plus or minus fifteen degrees.

We developed a prototype of a walking assist machine for the elderly or rehabilitants, which used a spatial parallel link mechanism. Its flat step moves in parallel with the ground and can support the whole legs of a person including his/her soles. To confirm the validity of our supporting method, muscle activity of the leg while wearing the machine was evaluated by using electromyography (EMG). Experimental results of measured muscle activities while slow-walking and wearing are shown.

We developed a prototype of a walking assist machine for the elderly or rehabilitants, which used a spatial parallel link mechanism. Its flat step moves in parallel with the ground and can support the whole legs of a person including his/her soles. To confirm the validity of our supporting method, muscle activity of the leg while wearing the machine was evaluated by using electromyography (EMG). Experimental results of measured muscle activities while slow-walking and wearing are shown.

Walking is the most important activity both for elderly people and rehabilitants to spend their daily life safely, comfortably and independently. Walking is the most fundamental movement and athletic ability. For the elderly people, walking especially contributes to improving and maintaining the muscle power, the respiratory and circulatory organ systems, and further walking is a valuable activity to prevent a bedridden condition. This paper proposes a walking assist machine for the elderly people, which use a new active-ankle-foot support machine. Its machine matched to the movement of foot joint. The prototype was developed, and the performance was evaluated.

A method for predicting gear noise produced by a gear system was developed. This method calculates the distribution of sound pressure around the gearbox and identifies the areas from which noise radiates intensely. According to the sound-power level calculated from this pressure distribution, a low-noise gearbox was designed by adding ribs. The appropriate adding points were then calculated from the viewpoint of mass variation. It was found that to decrease the noise, ribs should be added in two places: (i) along the line with maximum curvature through the antinode of the gearbox's vibration mode or (ii) the minimum-length line which crosses the most contour lines through the maximum point of the sound-pressure contour map. It was also found that in the case of a gearbox with a vibration mode in which the gearbox side faces vibrate in opposite directions, noise can be effectively reduced by connecting the ribs on both side faces.

A new method - utilizing gear-vibration analysis and finite-element-method (FEM) analysis - for calculating the three-dimensional-vibration behavior of a multi-stage helical gear system including a gearbox has been developed. First, to predict three-dimensional multi-stage helical gear vibration, each gear was modeled with six-DOF (degrees of freedom) ; three translational motions, and three swing motions. Stiffness matrices for each gear shaft and for each tooth meshing were made and overlapped into a stiffness matrix for the total system. Next, an FEM model of the gear system, which included separate models for the gearbox, gear shafts, gear meshings, bearings, and legs of the gearbox, was made. The results of a three-dimensional gear-vibration analysis were input into the model, to obtain the vibration responses of the gearbox. The calculated eigen frequencies and vibration responses of the gearbox agreed well with measured values.