Details of a Researcher - Takahashi, Masaki

Papers - Takahashi, Masaki

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Crater detection robust to illumination and shape changes using convolutional neural network

Ishida T., Takahashi M., Fukuda S.

Transactions of the Japan Society for Aeronautical and Space Sciences (Transactions of the Japan Society for Aeronautical and Space Sciences) 64 ( 4 ) 197 - 204 2021

ISSN 05493811

As a vast amount of data with respect to the moon and Mars is collected, exploration missions are shifting to the next step, the aim of which is a precise landing on a predetermined target. A promising technology for precision landing is terrain relative navigation (TRN), which collates landmarks detected from images and maps of landmarks. Crater detection is one of the essential technologies for TRN. A problem in detecting craters is the apparent change in craters due to illumination conditions. Another problem is the change in shape due to crater degradation. We propose a novel crater detection method based on combining a support vector machine (SVM) and a convolutional neural network (CNN) to make detection performance robust against apparent change. In the linear SVM, gradient images of a crater image dataset are learned. The learned classifier is then used to calculate the objectness score for region proposal. Next, the CNN identifies the image of the proposed region as to whether or not it is a crater. Our results show that the proposed method can detect craters in a wide range of illumination and shape conditions, and has better average precision than traditional crater detectors.

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Uncertainty-aware Non-linear Model Predictive Control for Human-following Companion Robot

Sekiguchi S., Yorozu A., Kuno K., Okada M., Watanabe Y., Takahashi M.

Proceedings - IEEE International Conference on Robotics and Automation (Proceedings - IEEE International Conference on Robotics and Automation) 2021-May 8316 - 8322 2021

ISSN 10504729

For a companion robot that follows a person as an assistant, predicting human walking is important to produce a proactive movement that is helpful to maintain an appropriate area decided by the human personal space. However, fully trusting the prediction may result in obstructing human walking because it is not always accurate. Hence, we consider the estimation of uncertainty (i.e., entropy) of the prediction to enable the robot to move without causing overconfident motion and without being late for the person it follows. To consider this uncertainty of the prediction to the controller, we introduce a reliability value that changes based on the entropy of the prediction. This value expresses the extent the controller should trust the prediction result, and it affects the cost function of our controller. We propose an uncertainty-aware robot controller based on nonlinear model predictive control to realize natural human-followings. We found that our uncertainty-aware control system can produce an appropriate robot movement, such as not obstructing the human walking and avoiding delay, in both simulations using actual human walking data and real-robot experiments.

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Transcutaneous Electrical Nerve Stimulation Improves Stair Climbing Capacity in People with Knee Osteoarthritis

Iijima H., Eguchi R., Shimoura K., Yamada K., Aoyama T., Takahashi M.

Scientific Reports (Scientific Reports) 10 ( 1 ) 2020.12

© 2020, The Author(s). This study aimed to examine the effect of transcutaneous electrical nerve stimulation (TENS) on stair climbing capacity in individuals with pre-radiographic to mild knee osteoarthritis (OA). This is a secondary analysis of data from a single, participant-blinded, randomized controlled trial with a pre-post design. Participants with pre-radiographic to mild knee OA (mean age, 59.1 years; 72.9% women) were randomly assigned into two groups, a TENS (n = 30) and a sham-TENS groups (n = 29). TENS or sham-TENS treatments were applied to all participants by using the prototype TENS device with pre-specified parameters. The primary outcome measures included valid and reliable functional measures for stair climbing (stair-climb test [SCT]), visual analog scale for knee pain during the SCT, and quadriceps muscle strength. TENS improved SCT time by 0.41 s (95% confidence interval [CI]: 0.07, 0.75). The time reduction in the transition phase explains the TENS therapeutic effect. Post-hoc correlation analyses revealed a non-significant but positive relationship between the pain relief effect and improved 11-step SCT time in the TENS group but not in the sham-TENS group. These results indicate that the TENS intervention may be an option for reducing the burden of early-stage knee OA.

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Dynamic Motion Tracking Based on Point Cloud Matching with Personalized Body Segmentation

Ono T., Eguchi R., Takahashi M.

Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics (Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics) 2020-November 61 - 67 2020.11

ISSN 9781728159072

Falling is a serious problem with the growing elderly population. In this sense, clinical institutions have implemented motor function assessment programs. In particular, the timed up and go test (TUG) is the most frequently applied clinical trial to assess the elderly walking ability in many clinical institutions and communities. In this study, we proposed a gait measurement system that can evaluate motor function in dynamic gait tests, such as the TUG test, using the point clouds of depth sensors (Kinect). The TUG test is a dynamic task that includes 3m of walking and turning motion. However, estimating joint positions using conventional methods that use Kinect skeleton function or point clouds is difficult. To solve these problems, before applying the iterative closest point algorithm, we proposed a method to move the segment model to a pre-estimated position and perform matching. In the accuracy verification experiments of several young people, the average error of each joint position was less than approximately 0.03 m, and the average error of the knee angle was approximately 4.54 to 5.13 degrees. These results indicate that the values estimated by the proposed method are useful as values for evaluating clinical tasks.

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Shift-Adaptive Estimation of Joint Angle Using Instrumented Brace with Two Stretch Sensors Based on Gaussian Mixture Models

Eguchi R., Michael B., Howard M., Takahashi M.

IEEE Robotics and Automation Letters (IEEE Robotics and Automation Letters) 5 ( 4 ) 5881 - 5888 2020.10

© 2016 IEEE. Wearable motion sensing in daily life has attracted attention in various disciplines. Especially, stretchable strain sensors have been instrumented into garments (e.g. brace). To estimate joint motions from such sensors, previous studies have modelled relationships between the sensor strains and motion parameters via supervised/semi-supervised learning. However, typically these only model a single relationship assuming the sensor to be located at a specific point on the body. Consequently, they exhibit reduced performance when the strain-parameter relationship varies due to sensor shifts caused by long-term wearing or donning/doffing of braces. This letter presents a shift-adaptive estimation of knee joint angle. First, a brace is instrumented with two stretch sensors placed at different heights. Next, the different strain-angle relationships at varying brace shift positions are learned using Gaussian mixture models (GMMs). The system then estimates the joint angle from the sensor strains through Gaussian mixture regression using a maximum likelihood shift GMM, which is identified by referring to the two strains in a previous 1 s period. Experimental results indicated that the proposed method estimates the joint angle at multiple shift positions (0-20 mm) with higher accuracy than methods using a single model, single sensor, or referring to the present sensor strains.

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Estimation of body direction based on gait for service robot applications

Yorozu A., Takahashi M.

Robotics and Autonomous Systems (Robotics and Autonomous Systems) 132 2020.10

ISSN 09218890

© 2020 Elsevier B.V. Recently, there have been several studies on the research and development of service robots, such as reception or waiter robots for facilities and companion robots for support of baggage transportation or guidance in public spaces. Several experimental results in real environments have been reported. To realize socially acceptable human–robot interaction for service robots, human recognition, including not only position but also body direction, around the robot is important. Using an RGB-D camera, it is possible to detect the posture of a person. However, because the viewing angle of the camera is narrow, it is difficult to recognize the environment around the robot with a single device. This study proposes the estimation of the body direction based on the gait, that is, not only the position and velocity, but also the state of the legs (stance or swing phase), using laser range sensors installed at shin height. We verify the effectiveness of the proposed method for several patterns of movement, which are seen when a person interacts with the service robot and evaluate measurement accuracy.

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Relationship Between Varus Thrust During Gait and Low Back Pain in Individuals With Knee Osteoarthritis

Iijima H., Suzuki Y., Aoyama T., Takahashi M.

Arthritis Care and Research (Arthritis Care and Research) 72 ( 9 ) 1231 - 1238 2020.09

ISSN 2151464X

Objective: To test the hypothesis that varus thrust visualized during gait is associated with a higher prevalence of low back pain (LBP) in individuals with knee osteoarthritis (OA). Methods: Individuals with knee OA (Kellgren/Lawrence grade ≥1) underwent a gait observation to assess varus thrust. The participants identified LBP and its severity using questionnaires. Logistic regression analyses were performed to examine the association between varus thrust and LBP. Results: We included 205 participants (mean age 68.19 years; 72.20% women). A total of 45 participants (22.0%) showed varus thrust in their painful knee, in whom 31 (68.89%) and 18 (40.00%) were identified as having any LBP and moderate-to-severe LBP (numerical rating scale ≥4 points), respectively. Patients with varus thrust demonstrated a 3.6-fold higher risk of the presence of moderate-to-severe LBP (95% confidence interval [95% CI] 1.62–8.10). In patients with LBP, the presence of varus thrust was associated with more severe LBP intensity (proportional odds ratio 2.25 [95% CI 1.02–4.96]). Conclusion: This study highlights the novel relationship between varus thrust and LBP, which supports the idea of a biomechanical link, the so-called knee–spine syndrome. These findings provide new insight for clarifying the pathogenesis of LBP related to knee OA.

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Human-friendly control system design for two-wheeled service robot with optimal control approach

Sekiguchi S., Yorozu A., Kuno K., Okada M., Watanabe Y., Takahashi M.

Robotics and Autonomous Systems (Robotics and Autonomous Systems) 131 2020.09

ISSN 09218890

© 2020 Elsevier B.V. This paper proposes a novel control system design for a two-wheeled service robot that follows a person as an assistant without knowing the person's destination. For this kind of service robot, the key skill is to realize human-friendly movement. However, appropriate motion always changed depending on the situation. For instance, when the robot is close and person turns toward it, it is important to suppress the robot's acceleration. Likewise, if the person turns away from the robot, the robot should maintain its position within an appropriate area. Therefore, to deal with various required movements, our control system is able to change its properties automatically and suitably depending on the situation by using weights of the cost function in nonlinear model predictive control (NMPC) as a function of the relative distance between the person and the robot. Unlike previous methods, our design includes only one controller. Consequently, we are able to take into account system stability. Moreover, owing to proposing in NMPC framework, it is easy to extend our method by adopting other recognition or goal-setting methods. We conducted simulations using actual human walking data taken by the robot's laser range sensors. The experiments demonstrate that the robot can follow a person who performs U-turn, confirming that our method can produce human-friendly robot movement in a practical scene.

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Gait analysis of patients with distal radius fracture by using a novel laser Timed Up-and-Go system

Fujita K., Iijima H., Eguchi R., Kuroiwa T., Sasaki T., Yokoyama Y., Koyama T., Nimura A., Kato R., Okawa A., Takahashi M.

Gait and Posture (Gait and Posture) 80 223 - 227 2020.07

ISSN 09666362

© 2020 The Authors Background: Postmenopausal women are at risk of fall and fracture with the physical decline. Distal radius fracture (DRF) is considered as the primary fragility fracture, and women with this fracture showed poor results in the usual Timed Up-and-Go (TUG) test, indicating a decline in balance and physical ability. The detailed physical characteristics of female DRF patients have not been extensively examined. Research question: Is the novel laser TUG system able to detect and analyze the detailed gait characteristics in patients with DRF whose physical ability has tended to decline? Methods: In this cross-sectional case control study, the gait characteristics of 32 female patients with DRF who had undergone surgery were evaluated at 2 weeks postoperatively with a laser TUG system to analyze the detailed leg motion during normal TUG test. Forty-three age- and sex-matched non-fractured women were evaluated by the laser TUG system as controls. Lifestyle and present illness were corrected at the time of TUG measurement. Detailed data during laser TUG in both groups were compared statistically, and odds ratio and thread shod of the fracture was elucidated through a logistic regression analysis. Results: DRF patients showed slower speed and had to do more steps to complete the TUG test. Furthermore, asymmetric trajectory and significantly further distance from the marker were observed. Thirteen steps to complete the TUG test was the thread shod of DRF. Significance: Detailed gait characteristics of patients with DRF were detected by the laser TUG system. The gait decline and abnormality could be one of the reasons of consecutive fragility fracture. To prevent secondary fragility fractures, this system can be useful for screening.

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Assessment of motion and muscle activation impacts on low back pain during pregnancy using an inertial measurement unit

Morino S., Yamashita M., Umezaki F., Hatanaka H., Takahashi M.

Applied Sciences (Switzerland) (Applied Sciences (Switzerland)) 10 ( 11 ) 2020.06

© 2020 by the authors. Specific physiological changes during pregnancy exert excessive strain on muscles such as the erector spinae (ES) and contribute to low back pain (LBP). The link between LBP and sit-to-stand (STS) motion has previously been investigated through motion analysis using an inertial measurement unit (IMU); however, the factors leading to LBP have not been revealed. Moreover, clinicians require an effective assessment method for reducing the physical burden on pregnant women. Therefore, the investigation of the relationships between motion, muscle load calculated from musculoskeletal model for pregnancy, and the severity of LBP during STS in pregnant women was conducted. Furthermore, this study proposes a method for assessing motion and muscle load during STS using an IMU. The relationship among (i) motion evaluation indices and ES muscle torque, and (ii) the ES torque and the intensity of LBP during STS was investigated. As the results, significant positive correlations were observed between (i) the angular velocity of the torso in the sagittal plane and ES torque, and (ii) two types of evaluation indices of ES torque and intensity of LBP. The proposed method by an IMU attached to the torso could effectively assess ES load related to LBP during STS in pregnant women.

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State of the Field of waist-mounted sensor algorithm for gait events detection: A scoping review

Iijima H., Takahashi M.

Gait and Posture (Gait and Posture) 79 152 - 161 2020.06

ISSN 09666362

© 2020 Elsevier B.V. Background: A waist-mounted sensor is an attractive option for detecting initial and end of foot contacts during gait in a clinical setting without disturbing the subject's natural gait. Research question: To examine the current state of the field regarding waist-mounted sensor algorithms for gait event detection during locomotion in adults. Methods: A scoping review design was used to search peer-reviewed literature or conference proceedings published through October 2018 for algorithms for gait event detection. We analyzed data from the studies in a descriptive manner. Results: In total, 588 potentially relevant articles were selected, of which 14 (171 participants, mean age: 44.0 years) met the inclusion criteria. We identified 15 algorithms developed using biomechanical theories including the inverted pendulum model that represents gait during level walking. Most algorithms estimated gait events using triaxial acceleration data with an absolute error of approximately 50–100 ms in healthy adults. However, there was a large amount of inter-trial heterogeneity, and only a few algorithms were validated in patients with neurological diseases. Lower gait speed reduced the accuracy of gait event estimation. Significance: There was no algorithm that showed outstanding performance in the estimation of gait events during level walking using the waist-mounted sensor. More comparisons of all available algorithms with an established reference standard for one data-set are needed to identify the best algorithms. As patients with pathological conditions display altered trunk acceleration and slower gait speeds, the development of an algorithm that does not rely on particular signal characteristics and is robust for a wide range of gait speeds is needed before a specific algorithm can be recommended as a valid strategy for clinical practice.

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Estimation of Vertical Ground Reaction Force Using Low-Cost Insole with Force Plate-Free Learning from Single Leg Stance and Walking

Eguchi R., Yorozu A., Fukumoto T., Takahashi M.

IEEE Journal of Biomedical and Health Informatics (IEEE Journal of Biomedical and Health Informatics) 24 ( 5 ) 1276 - 1283 2020.05

ISSN 21682194

© 2013 IEEE. For the evaluation of pathological gait, a machine learning-based estimation of the vertical ground reaction force (vGRF) using a low-cost insole is proposed as an alternative to costly force plates. However, learning a model for estimation still relies on the use of force plates, which is not accessible in small clinics and individuals. Therefore, this paper presents a force plate-free learning from a single leg stance (SLS) and natural walking measured only by the insoles. This method used a linear least squares regression that fits insole measurements during SLS to body weight in order to learn a model to estimate vGRF during walking. Constraints were added to the regression so that vGRF estimates during walking were of proper magnitude, and the constraint bounds were newly defined as a linear function of stance duration. Moreover, a lower bound for the estimated vGRF in mid-stance was added to the constraints to enhance estimation accuracy. The vGRF estimated by the proposed method was compared with force platforms for 4 healthy young adults and 13 elderly adults including patients with mild osteoarthritis, knee pain, and valgus hallux. Through the experiments, the proposed learning method had a normalized root mean squared error under 10% for healthy young and elderly adults with stance durations within a certain range (600-800 ms). From these results, the validity of the proposed learning method was verified for various users requiring assessment in the field of medicine and healthcare.

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Plucking motions for tea harvesting robots using probabilistic movement primitives

Motokura K., Takahashi M., Ewerton M., Peters J.

IEEE Robotics and Automation Letters (IEEE Robotics and Automation Letters) 5 ( 2 ) 3275 - 3282 2020.04

© 2016 IEEE. This letter proposes a harvesting robot capable of plucking tea leaves. In order to harvest high-quality tea, the robot is required to pluck the petiole of the leaf without cutting it using blades. To pluck the leaves, it is necessary to reproduce a complicated human hand motion of pulling while rotating. Furthermore, the rotation and pulling of the hand, and the time taken, vary greatly depending on conditions that include the maturity of the leaves, thickness of the petioles, and thickness and length of the branches. Therefore, it is necessary to determine the amount of translational and rotational movements, and the length of time of the motion, according to each situation. In this study, the complicated motion is reproduced by learning from demonstration. The condition is judged in terms of the stiffness of the branches, which is defined as the force received from the branches per unit length when the gripped leaf is slightly pulled up. Combining the learned motions probabilistically at a ratio determined by the branch stiffness, the appropriate motion is generated, even for situations where no motion is taught. We compared the motions generated by the proposed method with the motions taught by humans, and verified the effectiveness of the proposed method. It was confirmed by experiment that the proposed method can harvest high-quality tea.

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Hip abductor muscle weakness and slowed turning motion in people with knee osteoarthritis

Iijima H., Yorozu A., Suzuki Y., Eguchi R., Aoyama T., Takahashi M.

Journal of Biomechanics (Journal of Biomechanics) 101 2020.03

ISSN 00219290

© 2020 Elsevier Ltd Laser range sensor-based timed up and go (laser-TUG) test can evaluate performance in TUG subtasks (sit-to-walk [STW], walking a short distance, and turning). This study aimed to test the hypothesis that weaker hip abductor muscle strength is more significantly associated with slowed turning speed than with the other TUG subtasks (STW and straight walking) after controlling for quadriceps muscle strength in patients with knee osteoarthritis (OA). Community-dwelling participants with knee OA (Kellgren and Lawrence [K&L] grade ≥ 1; mean age, 68.6 years; 70.3% women) underwent laser-TUG. Spatiotemporal gait parameters in TUG and the TUG subtasks were evaluated as outcome measures. The isometric muscle strength of the hip abductor and quadriceps was measured using a hand-held dynamometer. Multiple linear regression analysis was performed to examine the relationship between muscle strength as an independent variable and spatiotemporal parameters as dependent variables. The relative importance of hip abductor muscle strength was determined using the percentages of unique variance. Participants with weaker hip abductor muscle strength demonstrated 0.094 m/s slower turning speed after adjustment for covariates including quadriceps muscle strength. The unique variance explained by hip abductor muscle strength in turning speed was 2.1%. However, no significant relationships were confirmed between weak hip abductor muscle strength and the time to perform TUG and the straight walking (forward and return) phase. These findings indicate that turning motion may be more sensitive to aggravated hip abductor muscle weakness and may show better response to hip muscle strengthening exercises. Longitudinal studies are warranted to elucidate this issue.

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Head-synced Drone Control for Reducing Virtual Reality Sickness

Watanabe K., Takahashi M.

Journal of Intelligent and Robotic Systems: Theory and Applications (Journal of Intelligent and Robotic Systems: Theory and Applications) 97 ( 3-4 ) 733 - 744 2020.03

ISSN 09210296

© 2019, Springer Nature B.V. Controlling a drone using head-mounted display induces virtual reality (VR) sickness. From previous research, it is known that angular velocity is one of the contributing factors to induce VR sickness, however for drones, linear motion and the interaction between linear and angular motion often occur during operation. In this research, we investigate the effect of each conditions experimentally and proposes a method of controlling a drone to reduce VR sickness. We designed a system that does not make user’s head fixed at one point but allows to move the head freely. At the same time, the head orientation and direction are synced with the drone’s attitude to reduce sensory conflict. Two controllers were compared: joystick control and head control. We tested with a real system and conducted experiments on subjects to verify its effect. The proposed controller reduced angular velocity in the frequency range 0.1 to 10 Hz where a vestibular system becomes most sensitive, and it is demonstrated that reducing sensory conflict contributes to the reduction of VR sickness.

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Contralateral Limb Effect on Gait Asymmetry and Ipsilateral Pain in a Patient with Knee Osteoarthritis: A Proof-of-Concept Case Report

Iijima H., Inoue M., Suzuki Y., Shimoura K., Aoyama T., Madoba K., Takahashi M.

JBJS case connector (JBJS case connector) 10 ( 1 ) 2020.01

CASE: A 77-year-old woman with knee osteoarthritis (OA) complained of right (ipsilateral) knee pain for more than 5 years with gait asymmetry. The OA and quadriceps muscle weakness were more severe in the left (contralateral) knee, but she had no pain. Bracing of the left knee led to decreased gait asymmetry, as determined with an inertial measurement unit, and reduced pain in the right knee. CONCLUSION: This case highlights the contralateral knee effect on ipsilateral chronic knee pain, possibly through gait asymmetry. These findings provide a mechanistic insight into knee OA-related pain in patients with gait asymmetry and suggest a new rehabilitative approach.

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Detailed analysis of the transverse arch of hallux valgus feet with and without pain using weightbearing ultrasound imaging and precise force sensors

Zeidan H., Ryo E., Suzuki Y., Iijima H., Kajiwara Y., Harada K., Nakai K., Shimoura K., Fujimoto K., Takahashi M., Aoyama T.

PLoS ONE (PLoS ONE) 15 ( 1 ) 2020.01

© 2020 Zeidan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background Hallux valgus is the most common forefoot deformity and affects the transverse arch structure and its force loading patterns. This study aims to clarify the differences in the transverse arch structure and the force under the metatarsal heads individually, between normal feet and hallux valgus feet, and between hallux valgus feet with pain and without pain. We further test the association between the parameters of the transverse arch and hallux valgus angle and between the parameters and pain in hallux valgus. Methods Women's feet (105 feet) were divided into normal group (NORM) and hallux valgus group (HVG); and further into subgroups: hallux valgus without pain (HV Pain (-)) and hallux valgus with pain (HV Pain (+)). Transverse arch height and metatarsal heads height were measured using weight-bearing ultrasound imaging. Force under the metatarsal heads was measured using force sensors attached directly on the skin surface of the metatarsal heads. The measurements were taken in three loading positions: sitting, quiet standing and 90% weight shift on the tested foot. Differences between the groups were compared using Student t-test and Wilcoxon Exact test. Multivariate logistic analysis with adjustment for physical characteristics was also conducted. Results Transverse arch height was significantly higher in HVG than in NORM in all positions; there were no significant differences between HV Pain (+) and HV pain (-). Lateral sesamoid wassignificantly higher in HVG and HV Pain (+) than in NORM and HV Pain (-) respectively when bearing 90% of the body weight unilaterally. There was a trend of higher forces under the medial forefoot without significant difference. Transverse arch height and lateral sesamoid height were associated with the hallux valgus angle, while lateral sesamoid height was associated with forefoot pain in hallux valgus deformity. Conclusions This study shows the differences in the transverse arch structure between normal feet and feet with hallux valgus, and between hallux valgus feet with and without pain. This finding is noteworthy when considering future treatments of painful feet, notably the height of the lateral sesamoid which seems to play a role in forefoot pain.

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Reducing speed commands in interval management with speed planning

Riedel T., Takahashi M., Itoh E.

Aeronautical Journal (Aeronautical Journal) 189 - 215 2020

ISSN 00019240

© 2019 Royal Aeronautical Society. Flight-deck Interval Management (FIM) is a modern airborne self-spacing technology that improves arrival route throughput and runway utilisation and increases hourly arrival capacity by up to four aircraft per hour and per runway, compared to conventional air traffic controller guided arrivals. The National Aeronautics and Space Administration (NASA) has been the leader in FIM research and formulated a logic that was put to an actual flight test in 2017. Despite the overall success of the project, operational deficiencies concerning the number of speed commands, which led to several recommendations for future research before operational implementation, were discovered. In this study, a new logic that implements a two-stage rule-based selection algorithm was developed to overcome those deficiencies. The proposed logic was compared to NASA's logic on an arrival in Tokyo International Airport with multiple induced error patterns. The results indicate that the new logic significantly decreases the number of speed commands with only minor aggravations in spacing performance. The results that highlight the strengths and weaknesses of both concepts are discussed, and an outlook on and ideas for future research on FIM and the proposed logic are presented.

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Optimal power management considering attitude control and battery deterioration control for spacecraft with vscmg/ipacs

Yoshihara H., Takahashi M.

AIAA Scitech 2020 Forum (AIAA Scitech 2020 Forum) 1 PartF 2020

ISSN 9781624105951

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Earth observation satellites repeatedly charge and discharge their batteries in harsh environments, where sunlight illumination and shade occur repetitively; thus, battery power deteriorates rapidly. In this study, variable speed control moment gyro (VSCMG) / integrated power and attitude control system (IPACS), which has both an attitude control function and an energy storage function, was used for a lithium-ion battery and a hybrid. We propose a control law that suppresses the chemical deterioration factor of the battery while achieving attitude control by cooperatively charging and discharging the required power. The proposed method calculates the commands of VSCMG/IPACS and the power distribution ratio of the battery and VSCMG/IPACS at the same time, for power distribution that accounts for the reference torque. The proposed method considers the torque error, the wheel angular velocity variation, and the wheel angular acceleration variation, to ensure attitude control performance. In addition, to suppress the deterioration factor of the battery, an evaluation function considering the SOC and C rate of the battery is designed. While constraints on the output power, motor, and battery are satisfied, we obtain the optimal solution that minimizes the evaluation function. Using the above algorithm, the proposed method can yield optimal power distribution and commands of VSCMG/IPACS.

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Model predictive control of autonomous drone considering model of birds aimed at inducing a flock of birds

Hamabe S., Takahashi M.

AIAA Scitech 2020 Forum (AIAA Scitech 2020 Forum) 1 PartF 2020

ISSN 9781624105951

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. In recent years, bird strikes are increasing with the increase in the number of airliner flights. Therefore, measures against bird strikes are required. Collisions between an aircraft and a flock of birds during takeoff and landing are numerous and can cause serious damage. Related works have been conducted to prevent entry of a flock of birds into the runway. The purpose of this study was to guide a flock of birds into avoiding the runway using an autonomous drone. Guidance was successful in simulations and experiments, provided that the drone was located near a flock of birds. Therefore, in this study, assuming that the drones are placed around the runway and far from the flock, we propose a control method to move the drone towards the flock and guide the birds to prevent bird strikes. In order to realize interception and guidance under such conditions, we predict the trajectories of the bird flock using a model of birds. Setting the target position of the drone on the predicted trajectories allows the drone to intercept the birds without unnecessary movement of the drone. Because the drone is in the same speed range as the birds, we determine the drone’s control input so as to satisfy the velocity constraint using model predictive control (MPC). In this study, we propose a control method for autonomous drones that considers the model of birds, aimed at guiding a flock of birds to prevent bird strike. We verify the performance of the proposed method by conducting numerical analysis based on a model of a realistic runway.

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