Larger Reaction Force Research Articles

Decoupled 3D moment control using in-wheel motors

Vehicles equipped with in-wheel motors are being studied and developed as a type of electric vehicle. Since these motors are attached to the suspension, a large vertical suspension reaction force is generated during driving. Based on this mechanism, this paper describes the development of a method for independently controlling roll and pitch as well as yaw using driving force distribution control at each wheel. It also details the theoretical calculation of a method for decoupling the dynamic motions. Finally, it describes the application of these 3D dynamic motion control methods to a test vehicle and the confirmation of the performance improvement.

地震入力レベルを考慮した連結機構摩擦ダンパーの免震戸建て住宅への適用性

For the extremely large or the long period ground motions, it is feared that the base isolation layer collides with the side wall due to the extremely large displacement. In case dampers with large capacity are incorporated with the base isolation layer, the effect of the base isolation decreases due to the large reaction force of dampers in small seismic events. To realize the control of the displacement and the acceleration which is the important factor of the base isolation effect, the friction damper with coupling mechanism is proposed. Analytical studies are conducted using the base isolated detached houses with slide bearings and the proposed dampers. To decide a series of damper parameters, the optimum design method is used. Results indicate that the friction damper with coupling mechanism can control the maximum displacement and the maximum acceleration within the design criteria which is decided individually for the input ground motion level.

Impedance Control and its Effects on a Humanoid Robot Playing Table Tennis

This paper proposes an impedance control scheme used on humanoid robots for stability maintenance when the robot is expected to carry out fast manipulatory tasks. We take table tennis playing as an example to study this issue. The fast acceleration required by table tennis rallying will result in an unknown large reaction force on the robot, causing the body to swing back and forth in an oscillating motion and the foot to lose complete contact with the ground. To improve the stability during fast manipulation and in order to resist disturbances due to the reaction force, we introduce impedance control to absorb the impact and decrease the amplitude of body swinging. The system's adjusting time is also reduced and the oscillations are eliminated according to the experimental results, which show the effectiveness of our scheme.

Independent control of force and timing symmetry in dynamic standing balance: Implications for rehabilitation of hemiparetic stroke patients

The extent to which force and timing are independently controlled has aroused research interest. The present study aims to examine the relationship between force and timing symmetrical performances during repetitive body weight shifting. Eight hemiparetic stroke patients and eight age- and gender-matched controls were required to repetitively shift weight from one leg to the other while standing with each foot on a separate force plate. Instructions emphasised symmetry of weight transfer in each direction. No knowledge of result feedback was given. The ratio of the vertical ground reaction forces between the legs (force symmetry) was contrasted with the ratio of the intervals between leftward and rightward movements (timing symmetry). The patients showed more asymmetric and variable performances than the controls. Timing symmetry was more variable than force symmetry. In both groups, force and timing symmetry were uncorrelated. Autocovariance estimates revealed persistent alternation of large and small ground reaction forces, whereas a tendency for alternation between short and long intervals rapidly damped to zero. In conclusion, both healthy and stroke participants exhibit independent control of the force and timing symmetry under the task of natural weight shifting. This may explain the weakness of current balance retraining paradigms based on visual biofeedback, in which an emphasis on force symmetry fails to help timing performance in dynamic tasks.

CHANGES IN MEDIO-LATERAL KNEE JOINT REACTIONS OF FLATFOOT PATIENTS DUE TO INSOLE CONDITIONS

The flattened foot arch causes the mechanical overloading transferred to proximal areas (i.e. ankles, knees, or hips) over time. Thus, the flatfoot is recognized as a contributory factor in a wide variety of musculo-skeletal pathologies in lower extremities. Commonly, flatfoot deformities are treated using specially designed insoles that support the arch and correct the posture of lower limbs. However, the biomechanical effects of the insoles are not yet fully understood, so there still are controversies whether such insoles really have clinical significance [Chen, 2010]. In this study, in order to verify the effects of insoles and determine the best shape of the insoles, we examined how the medio-lateral knee joint reaction force changes due to insole conditions. Since large knee joint reaction force is one of major causes of knee osteoarthritis or knee pain [Radin, 1991], our study will be beneficial in prescribing insoles to prevent knee pathologies of flatfoot patients.

사각에 따른 RC슬래브교의 반력특성 분석

본 연구에서는 2경간 연속 RC 슬래브교를 대상으로 차량 이동하중 시간이력해석을 수행하여 사각에 따른 받침의 반력분포 특성을 분석하였다. 계측값과 해석값의 비교를 통해 적용 시간이력해석방법을 검증하였으며, 사각을 매개변수로 판 해석을 수행한 결과, 둔각부 최외측 받침에 반력이 집중되며, 사각이 감소함에 따라(사교의 정도가 커질수록) 반력의 편차가 커져 둔각부에 반력의 크기가 증가하는 것으로 나타났다. 또한, 반력이 집중된 최외측 받침의 인접 받침에서는 사각 <TEX>$70^{\circ}$</TEX> 이하에서 부반력이 발생하는 것으로 분석되었다. 따라서 사각을 갖는 RC 슬래브교에서는 받침의 용량 산정 시 반력의 편차와 부반력 발생에 유의하여야 한다고 판단된다. The support reactions of two-span RC slab bridges with various skews are studied through the time history analysis for moving vehicles. Dynamic behaviors of bridges are evaluated by using the commercial FEM code and the bridge is modelled using shell elements. The analysis method is verified by comparing measured values and analysis results. Parametric analysis are performed for various skew angles. The bearing below the end slab with an obtuse angle shows the largest reaction forces. As the skew angle is reduced(a skew angle of <TEX>$90^{\circ}$</TEX> means a straight bridge without skew in this study), the distribution of reaction force is growing uneven and the largest reaction force is increased. In case of the model having skew angles under <TEX>$70^{\circ}$</TEX>, the bearing located near the bearing with the largest reaction force shows the uplift force. Thus, it is concluded that the bearing in RC slab bridges with skew should be selected carefully by considering the variation of reaction force and uplift force.

Investigation of Spinal Posture Signatures and Ground Reaction Forces During Landing in Elite Female Gymnasts

The link between static and dynamic landing lumbar postures, when gymnasts are exposed to large ground reaction forces, has not been established. This investigation aimed to (a) determine if a relationship exists between sagittal static and dynamic landing lumbar spine angles at peak ground reaction force (GRF) and (b) quantify how close to end-range postures the gymnasts were at landing peak GRF. Twenty-one female gymnasts' upper and lower lumbar spine angles were recorded: statically in sitting and standing, during landing of three gymnastic skills, and during active end-range lumbar flexion. Pearson's correlations were used to investigate relationships between the angles in different postures. Significant correlations (r = .77-.89, p <.01) were found between all the static/dynamic postures in the lower lumbar spine angle, while fewer and less significant upper lumbar spine correlations were reported. Thirty percent of gymnasts landed a backsault with their lower lumbar spine flexed beyond their active end-range while experiencing GRF 6.8-13.3 times their body weight. These results inform low back pain prevention and management strategies in this population and highlight areas for future research.

The Design of Roof Structure for Bicycle Stadium in Jinan Olympic Sports Center

Bicycle Stadium in Jinan Olympic Sports Center adopts spatial truss structure with steel tube. The design and analysis of the roof structure are introduced in detail. By applying the program SAP2000 and STCAD, the static and dynamic properties of the roof structure are obtained. In addition, the design of the cast steel support joint are studied, which focuses on analyzing the static behavior of the typical cast steel support by using the program ANSYS. The results prove that the spatial truss structure is reasonable, which can satisfy the requirements of safety of the building. For the complex support joints subjected to large reaction forces, cast steel support joints can meet the architectural and structural requirements. The research results in this paper can provide references for the design of similar engineering.

The effect of choice reaction task on impact of single-leg landing

This study aimed to investigate attentional demand during single-leg landing after a jump. The experiment was set up as dual-task test. Twelve healthy male participants were instructed to make a two-leg jump with right-leg landing as softly as possible. The flight time of the jump was set to 300ms through sufficient practice. As a cognitive task, the participants were asked to push the right or left custom-made button as soon as a go-signal was presented. The timing when the go-signal presented varied from 0 to 300ms from the take-off. Catch trials in which the go-signal was not presented were randomly inserted. The results showed that the maximum vertical ground reaction force after touchdown was greater under the dual-task condition than in the single-task condition. Increase in the maximum vertical ground reaction force was consistent regardless of the timing of presenting the go-signal, and the same effect was observed in the catch trials. These results indicate that the effect of dual tasking was caused by attentional allocation to the choice reaction time task. Athletes may be exposed a large ground reaction forces during landing while performing cognitive tasks.

Functional anatomy of the cheetah (Acinonyx jubatus) forelimb

Despite the cheetah being the fastest living land mammal, we know remarkably little about how it attains such high top speeds (29 m s(-1)). Here we aim to describe and quantify the musculoskeletal anatomy of the cheetah forelimb and compare it to the racing greyhound, an animal of similar mass, but which can only attain a top speed of 17 m s(-1). Measurements were made of muscle mass, fascicle length and moment arms, enabling calculations of muscle volume, physiological cross-sectional area (PCSA), and estimates of joint torques and rotational velocities. Bone lengths, masses and mid-shaft cross-sectional areas were also measured. Several species differences were observed and have been discussed, such as the long fibred serratus ventralis muscle in the cheetah, which we theorise may translate the scapula along the rib cage (as has been observed in domestic cats), thereby increasing the cheetah's effective limb length. The cheetah's proximal limb contained many large PCSA muscles with long moment arms, suggesting that this limb is resisting large ground reaction force joint torques and therefore is not functioning as a simple strut. Its structure may also reflect a need for control and stabilisation during the high-speed manoeuvring in hunting. The large digital flexors and extensors observed in the cheetah forelimb may be used to dig the digits into the ground, aiding with traction when galloping and manoeuvring.

Ankle-Dorsiflexion Range of Motion and Landing Biomechanics

A smaller amount of ankle-dorsiflexion displacement during landing is associated with less knee-flexion displacement and greater ground reaction forces, and greater ground reaction forces are associated with greater knee-valgus displacement. Additionally, restricted dorsiflexion range of motion (ROM) is associated with greater knee-valgus displacement during landing and squatting tasks. Because large ground reaction forces and valgus displacement and limited knee-flexion displacement during landing are anterior cruciate ligament (ACL) injury risk factors, dorsiflexion ROM restrictions may be associated with a greater risk of ACL injury. However, it is unclear whether clinical measures of dorsiflexion ROM are associated with landing biomechanics. To evaluate relationships between dorsiflexion ROM and landing biomechanics. Descriptive laboratory study. Research laboratory. Thirty-five healthy, physically active volunteers. Passive dorsiflexion ROM was assessed under extended-knee and flexed-knee conditions. Landing biomechanics were assessed via an optical motion-capture system interfaced with a force plate. Dorsiflexion ROM was measured in degrees using goniometry. Knee-flexion and knee-valgus displacements and vertical and posterior ground reaction forces were calculated during the landing task. Simple correlations were used to evaluate relationships between dorsiflexion ROM and each biomechanical variable. Significant correlations were noted between extended-knee dorsiflexion ROM and knee-flexion displacement (r = 0.464, P = .029) and vertical (r = -0.411, P = .014) and posterior (r = -0.412, P = .014) ground reaction forces. All correlations for flexed-knee dorsiflexion ROM and knee-valgus displacement were nonsignificant. Greater dorsiflexion ROM was associated with greater knee-flexion displacement and smaller ground reaction forces during landing, thus inducing a landing posture consistent with reduced ACL injury risk and limiting the forces the lower extremity must absorb. These findings suggest that clinical techniques to increase plantar-flexor extensibility and dorsiflexion ROM may be important additions to ACL injury-prevention programs.

Fastening ergonomics study based on state-space modelling of hand-arm system

The aim of this study is to model the hand-arm as a rotational single-degree-of-freedom system during fastening operations with shear-type fasteners using state-space representation. The values of the model parameters are estimated by determining the characteristic state-space matrices from the measured tool rotation and torque data collected during the fastening operation and then using a parameter extraction algorithm to derive the model parameters in the state-space matrices. The identified parameter values are used to determine the response and the dynamic reaction force, which are used to assess the dynamic effects of tool operation on the hand-arm. The effect of posture, grip-force and tool-type variation is analysed using the dynamic reaction force. Strong agreements are observed between the predicted and measured responses. The model parameter values increase with an increase in grip force and vary significantly for the two tools and four postures studied. The pistol-grip tool generates larger reaction force than the right-angled tool.

Effects of a Knee Extension Constraint Brace on Lower Extremity Movements after ACL Reconstruction

Patients have high reinjury rates after ACL reconstruction. Small knee flexion angles and large peak posterior ground reaction forces in landing tasks increase ACL loading. We determined the effects of a knee extension constraint brace on knee flexion angle, peak posterior ground reaction force, and movement speed in functional activities of patients after ACL reconstruction. Six male and six female patients 3.5 to 6.5 months after ACL reconstruction participated in the study. Three-dimensional videographic and force plate data were collected while patients performed level walking, jogging, and stair descent wearing a knee extension constraint brace, wearing a nonconstraint brace, and not wearing a knee brace. Knee flexion angle at initial foot contact with the ground, peak posterior ground reaction force, and movement speed were compared across brace conditions and between genders. Wearing the knee extension constraint brace increased the knee flexion angle at initial foot contact for each activity when compared with the other two brace conditions. Wearing the knee extension constraint brace also decreased peak posterior ground reaction force during walking but not during jogging and stair descent. Although the knee extension constraint brace did not consistently reduce the peak posterior ground reaction force in all functional activities, it consistently increased knee flexion angle and should reduce ACL loading as suggested by previous studies. These results suggest the knee extension constraint brace has potential as a rehabilitation tool to alter lower extremity movement patterns of patients after ACL reconstruction to address high reinjury rates.

On the Horizon From the ORS

On the Horizon From the ORS

Asymmetric trajectory generation and impedance control for running of biped robots

An online asymmetric trajectory generation method for biped robots is proposed to maintain dynamical postural stability and increase energy autonomy, based on the running stability criterion defined in phases. In a support phase, an asymmetric trajectories for the hip and swing leg of the biped robots is obtained from an approximated running model with two springless legs and a spring-loaded inverted pendulum model so that the zero moment point should exist inside the safety boundary of a supporting foot, and the supporting leg should absorb large reaction forces, take off and fly through the air. The biped robot is under-actuated with six degrees of under-actuation during flight. The trajectory generation strategies for the hip and both legs in a flight phase use the approximated running model and non-holonomic constraints based on the linear and angular momenta at the mass center. Next, we present an impedance control with a force modulation strategy to guarantee a stable landing on the ground and simultaneously track the desired trajectories where the desired impedance at the hip link and both legs is specified. A series of computer simulations for two different types of biped robots show that the proposed running trajectory and impedance control method satisfy the two conditions for running stability and make the biped robot more robust to variations in the desired running speed, gait transitions between walking and running, and parametric modeling errors. We have examined the feasibility of this method with running experiments on a 12-DOF biped robot without arms. The biped robot could run successfully with average forward speed of about 0.3359 [m/s].

20614 武道における身体動作と軸足動的挙動の関係(スポーツ・福祉工学,一般講演,学術講演)

In this study, impact force measurements and biomechanical analysis were carried out during the KERI (kicking) of SHORINJI-KEMPO. The impact force and kinetic parameters were measured by using the proposed impact force measuring device with strain gages, accelerometer and the three-dimension rate gyro sensor. Furthermore, the force of pivot leg was measured by a 6 degree-of-freedom force sensor, and the movements of KERI-ASHI(moving leg during KERI motion)were measured by using accelerometer. The trained SHORINJI-KEMPO players showed the larger impact force in contrast to that for the un-trained player. The impact force was affected by the pivot leg movements. It is important to increase the impact force that the player supports the body with the toe side and the inside of the pivot leg and the body is stabilized by the large reaction force of pivot foot when the player starts the KERI motion.

B2 少林寺拳法における効果的な衝撃力向上に関する研究(動作解析1)

In the present study, impact force measurements and biomechanical analysis were carried out during the KERI (kicking) of SHORINJI-KEMPO. The impact force and kinetic parameters were measured by using the proposed impact force measuring device with strain gages, accelerometer and three-dimensional rate gyro sensors. Furthermore, the force of pivot leg was measured by a 6 degree-of-freedom force sensor, and the movements of KERI-ASHI (moving leg during KERI motion) were measured by using accelerometer. The trained SHORTNJI-KEMPO players showed the larger impact force in contrast to that for un-trained players. The impact force was affected by the pivot leg movements. It is important to increase the impact force that the player supports the body with the toe side and the inside of the pivot leg and the body is stabilized by the large reaction force of pivot foot when the player starts the KERI motion.

2P1-I23 2足歩行ロボットの基礎研究 : 合成重心軌道と床反力の制御(アミューズメント・エンタティナーロボット)

Recently researches of biped running robots are increasing. These researches deal with low-velocity running such as jogging. As the running velocity becomes higher, the ground reaction force including impact force at touch down becomes larger than that of low-velocity running. The large reaction force makes the robot unstable. Therefore, in high-speed running, the control of the ground reaction force is very important. In this study, we modeled the ground as a dynamical model of two springs and a dashpot. The model can make the reaction force curve during the landing period just the same as that of a human athlete. The trajectories of the joint angles are derived so that the mass center of the whole body might change like a human athlete during the landing period.

Bearing Capacity in Long-Span Tubular Truss Chords

Existing design specifications used in the United States and abroad do not address the limit state of bearing failure that may govern in the design of tubular truss chords at the supports. The lack of treatment of this limit state seems to represent an unsatisfactory situation given the fact that very large concentrated reaction forces are often applied transversely to the ends of chord members with slender circular cross sections; long-span overhead highway sign trusses are but one example of an affected application. The bearing failure limit state is manifest as a coupled failure mechanism, consisting of a plastic collapse of the chord end and local plastification of the chord wall. In order to better understand this limit state, two full-scale experimental tests are conducted at the University of Pittsburgh as part of the current research. The specimens considered are proportioned to be representative of the bearing region of an overhead sign structure that failed in the limit state under investigation. These tests yield important information regarding the manifestation of the bearing limit state and also afford an opportunity to verify finite element modeling techniques for use in a parametric study. The parametric study reveals that the bearing capacity is influenced by many factors including the geometry of the bearing connection, the adjacent intermediate truss member, the nature of loading, and the material properties. Using regression analysis on the parametric study results and concepts from the yield line method for analyzing collapse mechanisms, general equations for predicting the bearing capacity are developed.

A Finite Element Scheme for Impact Force Prediction of Robotic Mechanisms

Stress in robots operating at high speed may be considerable. Robots can also be subjected to unexpected, large reaction forces that may not be detected by sensors during high-speed impact. These present major problems since impact may damage the robotic mechanism. We propose the concept of impact force prediction using numerical models and a low-cost finite element scheme considering inertia and large motion of the whole system. We developed a scheme using gap elements to simulate the contact-impact phenomenon. To check the scheme’s validity, we conducted tests and experiments whose results show that impact analysis considering the stiffness of contact objects is possible. Peak of impact forces in numerical analysis agrees well with those of experiments.