Robot navigation in orchards with localization based on Particle filter and Kalman filter

Blok, Pieter M.,van Boheemen, Koen,van Evert, Frits K.,IJsselmuiden, Joris,Kim, Gook-Hwan Elsevier 2019 Computers and electronics in agriculture Vol.157 No.-

<P><B>Abstract</B></P> <P>Fruit production in orchards currently relies on high labor inputs. Concerns arising from the increasing labor cost and shortage of labor can be mitigated by the availability of an autonomous orchard robot. A core feature for every mobile orchard robot is autonomous navigation, which depends on sensor-based robot localization in the orchard environment. This research validated the applicability of two probabilistic localization algorithms that used a 2D LIDAR scanner for in-row robot navigation in orchards. The first localization algorithm was a Particle filter (PF) with a laser beam model, and the second was a Kalman filter (KF) with a line-detection algorithm. We evaluated the performance of the two algorithms when autonomously navigating a robot in a commercial Dutch apple orchard. Two experiments were executed to assess the navigation performance of the two algorithms under comparable conditions. The first experiment assessed the navigation accuracy, whereas the second experiment tested the algorithms’ robustness. In the first experiment, when the robot was driven with 0.25 m/s the root mean square error (RMSE) of the lateral deviation was 0.055 m with the PF algorithm and 0.087 m with the KF algorithm. At 0.50 m/s, the RMSE was 0.062 m with the PF algorithm and 0.091 m with the KF algorithm. In addition, with the PF the lateral deviations were equally distributed to both sides of the optimal navigation line, whereas with the KF the robot tended to navigate to the left of the optimal line. The second experiment tested the algorithms’ robustness to cope with missing trees in six different tree row patterns. The PF had a lower RMSE of the lateral deviation in five tree patterns. In three out of the six patterns, navigation with the KF led to lateral deviations that were biased to the left of the optimal line. The angular deviations of the PF and the KF were in the same range in both experiments. From the results, we conclude that a PF with laser beam model is to be preferred over a line-based KF for the in-row navigation of an autonomous orchard robot.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two localization algorithms compared in a Dutch apple orchard using Husky robot. </LI> <LI> Two experiments assessed navigation accuracy and navigation robustness. </LI> <LI> Particle filter outperformed Kalman filter on navigation accuracy and robustness. </LI> <LI> Algorithms are applicable for autonomous robot navigation using a 2D LIDAR scanner. </LI> </UL> </P>

Facilitators and Barriers in the Use of a Checklist by Insurance Physicians during Work Ability Assessments in Depressive Disorder

Blok, Sebastiaan,Gouttebarge, Vincent,Slebus, Frans G.,Sluiter, Judith K.,Frings-Dresen, Monique H.W. Occupational Safety and Health Research Institute 2011 Safety and health at work Vol.2 No.4

Objectives: Depressive disorder (DD) is a complex disease, and the assessment of work ability in patients with DD is also complicated. The checklist depression (CDp) has recently been developed to support such work ability assessments and has been recommended for implementation in insurance medicine, starting with an analysis of the organisational and social contexts. The aim of this study was to identify the potential facilitators and barriers in the use of the CDp by insurance physicians (IPs) during work ability assessments of employees on sick leave due to DD. Methods: A qualitative research was conducted based on semi-structured interviews. The participants were IPs with at least one year of work experience in performing work ability assessments. The interviews were audiotaped, transcribed and analysed qualitatively. Results: Ten IPs (7 males, 3 females; mean 53 years) were interviewed. Important facilitators, which emerged for use of the CDp, were an oral introduction for colleagues and staff, support from management, valuing the increased transparency in work ability assessments with using the CDp, having adequate time for assessments as well as modification of the appearance (colour, plasticised form) and content (clarifying aspects of the examples) of the assessment tool. The fear of the loss of autonomy, lack of added value of the CDp, high workload, inadequate instructions and lack of time were mentioned as barriers. Conclusion: Adequate introduction to the use of CDp and the fear of the loss of autonomy of IPs need special attention in planning its implementation.

Automatic Sugar Beet Phenotyping in Open Field by a Computer Vision System

( Pieter M. Blok ),( Jochen Hemming ),( Youngki Hong ),( Jaesu Lee ),( Daehyun Lee ),( Gookhwan Kim ) 한국농업기계학회 2016 한국농업기계학회 학술발표논문집 Vol.21 No.2

Crop growth is an important quality assessment in plant breeding, especially in open field crops which grow in fluctuating and unfavorable outdoor conditions. To evaluate the growth potential of different plant varieties, researchers conduct leaf area measurements of emerged plants to evaluate its growth potential. This is a time consuming and labor intensive activity and therefore often only conducted on random spots on the field. An automatic computer vision system was built to automate and to speed up this plant phenotyping process. The system consist of three color cameras mounted on an implement facing straight downwards, lamps for illumination, an encoder wheel and a computer system. Natural light was blocked by a surrounding cover to limit the effect of variable outdoor light conditions on the image quality. The computer vision software makes use of an excessive green algorithm (2G - R - B) to segment the plant material from the soil. As the crop plants are sown by a precision sowing device in a regular pattern a method based on the fast-fourier transform (FFT) is used to distinguish crop plants from weed plants. A rectangular based clustering algorithm, based on 8-pixel nearest-neighbor connectivity, is used to cluster separated plant-parts together as one individual plant object used to measure the leaf area. The system was validated in an open-field sugar beet crop at the growing stage off our leaves. Fifty-five sugar beet plants were manually measured by experienced plant scouts(“ground truth”). The same plants were measured with the computer vision system. An ANOVA F-test(P<0.05) was used to discriminate the two measurement methods. The F-probability was 0.055 an djust above the significance level. So the H0 hypothesis that there is not a difference between human measurement and machine vision measurement was no trejected. Possible causes of difference was the inability of the system to detect and measure plants damaged by animals and very small plants which were occluded by clods or bigger plants. Nevertheless,with improvements on the vision software and camera/lamp configuration, the system is profitable for a fast and accurate leaf area measurement and corresponding plant phenotyping.

2D LIDAR 스캐너와 파티클 필터 레이저빔 모델 기반의 과수 로봇의 주간 내 자율주행

Pieter M. Blok,서현권(Hyun Kwon Suh),Koen van Boheemen,김학진(Hak-Jin Kim),김국환(Gook-Hwan Kim) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.8

In mountainous orchards, agricultural tasks, such as crop protection and harvesting, are characterized as being labor intensive and dangerous. An autonomous orchard robot that can execute these unattended seems a promising alternative to increase task operability. An essential function in the development of an autonomous orchard robot is navigation, which is usually based on tree-row detection from LIDAR scan data by using navigational algorithms. This research applies a probabilistic particle filter (PF) algorithm with a novel laser-beam model for the autonomous in-row navigation of an orchard robot. The navigational accuracy of the algorithm is assessed in a Dutch apple orchard over a distance of 500 m, with the robot driving at two velocities: 0.25 m/s and 0.50 m/s. At both speeds, almost 50% of the observed lateral deviations were lower than 0.05 m from the optimal navigation line. With the use of the PF algorithm, the robot navigated itself between six patterns of tree rows with artificially removed trees. Some lateral deviations exceeded 0.10 m when three adjacent trees were missing in both tree rows. Based on these results, a PF with a laser beam model is an accurate and robust algorithm for the autonomous in-row navigation in semi-structured outdoor environments, such as orchards.

이차원 레이저 센서와 파티클 필터가 장착된 과원 로봇의 자율 항법 정확도 평가

( Pieter M. Blok ),( Koen Van Boheemen ),김국환 ( Gookhwan Kim ),이대현 ( Daehyun Lee ),홍영기 ( Youngki Hong ) 한국농업기계학회 2017 한국농업기계학회 학술발표논문집 Vol.22 No.2

과원에서 과실을 재배 할 때 직면하게 되는 어려움 중 하나는 효율적인 잡초 방제, 즉 제초 작업이다. 제초 작업은 종종 트랙터와 잔디 깎기 기계로 수행되는데 이 작업의 노동 집약적 특성으로 인해 그 빈도를 최소로 할 필요가 있다. 자율 주행이 가능한 로봇 플랫폼의 개발은 대규모 노동 투입 없이 정기적으로 과수원에서 잡초를 제거 할 수 있게 해준다. 과원 로봇의 설계에 있어 중요한 것은 장착되는 센서들을 활용하여 탐색 및 주행에 연관된 최적의 알고리즘 조합을 개발하여 수동 조종하는 현재의 제초 방법과 유사하거나 더 높은 항법 정확도를 제공해야 한다. 본 연구의 목적은 과원 로봇의 자율 항법을 위한 센서 및 알고리즘 조합의 최적화 및 정확성을 평가하여 신뢰성을 보고자 하였다. 자율 항법 알고리즘의 검증을 위한 테스트를 위한 로봇 플랫폼은 Clearpath Robotics사의 Husky A200로봇을 사용하였다. 이 로봇에는 장애물 및 과수열을 검출하기 위한 이차원 레이저 거리 센서(laser range finder, LRF), 로봇의 자세측정 및 데이터 보정을 위한 3축 관성측정장치(inertial measurement unit, IMU), 로봇의 주행 거리 및 속도를 추정하기 위한 바퀴 주행 측정기(odometry) 및 로봇의 자율 항법 알고리즘에 대한 정확도 검증을 위하여 고정도의 실시간 위성 항법 시스템(RTK-GNSS)가 장착되었다. 과수열 및 장애물 탐색 알고리즘은 파티클 필터(particle filter)를 기반으로 알고리즘을 구축하였다. 알고리즘 평가를 위한 실험은 네덜란드에 있는 사과 과원에서 수행하였다. 로봇에 적용한 파티클 필터 기반의 알고리즘 검증을 위하여 RTK-GNSS를 사용하여 정확한 로봇의 현재 위치를 파악하여 양 쪽에 심겨진 과수열을 따라 로봇이 얼마나 잘 추종하고 있는지를 기준 경로에 대한 편차 및 각도 편차를 계산하는 방식으로 수행하였다. 기준 경로와 비교하여 파티클 필터가 장착된 로봇은 속도가 0.25 m/s일 때, 평균 편차는 0.07 m, 평균 각도 편차는 2.57°였고, 0.5 m/s의 속도일 때는 0.08 m, 1.73°였다. 이차원 레이저 센서와 파티클 필터를 사용한 항법 알고리즘은 수동 조종하는 로봇의 대안으로 과원에서 과수열을 따라 자율 주행하는 것이 적합함을 입증하였다. 선회 구간 검출 및 장애물 회피는 이 연구에서 고려되지 않았으며 추후 개발되어 로봇에 탑재할 예정이다.

Separated response functions in exclusive, forward^π±electroproduction on deuterium

Huber, G. M.,Blok, H. P.,Butuceanu, C.,Gaskell, D.,Horn, T.,Mack, D. J.,Abbott, D.,Aniol, K.,Anklin, H.,Armstrong, C.,Arrington, J.,Assamagan, K.,Avery, S.,Baker, O. K.,Barrett, B.,Beise, E. J.,Bochna American Physical Society 2015 PHYSICAL REVIEW C - Vol.91 No.1

Gas dynamics and star formation in NGC 6822

Hye-Jin Park,Se-Heon Oh,Jing Wang,Yun Zheng,Hong-Xin Zhang,W J G de Blok 한국천문학회 2021 天文學會報 Vol.46 No.2

Gas kinematics and star formation in NGC 6822

Hye-Jin Park,Se-Heon Oh,Jing Wang,Yun Zheng,Hong-Xin Zhang,W.J.G. de Blok 한국천문학회 2020 天文學會報 Vol.45 No.1

Transcutaneous Electrical Stimulation of the Abdomen, Ear, and Tibial Nerve Modulates Bladder Contraction in a Rat Detrusor Overactivity Model: A Pilot Study

Rosa L. Coolen,Dennis Frings,Els van Asselt,Jeroen R. Scheepe,Bertil F. M. Blok 대한배뇨장애요실금학회 2023 International Neurourology Journal Vol.27 No.3

Purpose: The global prevalence of overactive bladder (OAB) is estimated at 11.8%. Despite existing treatment options such as sacral neuromodulation, a substantial number of patients remain untreated. One potential alternative is noninvasive transcutaneous electrical stimulation. This form of stimulation does not necessitate the implantation of an electrode, thereby eliminating the need for highly skilled surgeons, expensive implantable devices, or regular hospital visits. We hypothesized that alternative neural pathways can impact bladder contraction. Methods: In this pilot study, we conducted transcutaneous electrical stimulation of the abdominal wall (T6-L1), the ear (vagus nerve), and the ankle (tibial nerve) of 3 anesthetized female Sprague-Dawley rats. Stimulation was administered within a range of 20 Hz to 20 kHz, and its impact on intravesical pressure was measured. We focused on 3 primary outcomes related to intravesical pressure: (1) the pressure change from the onset of a contraction to its peak, (2) the average duration of contraction, and (3) the number of contractions within a specified timeframe. These measurements were taken while the bladder was filled with either saline or acetic acid (serving as a model for OAB). Results: Transcutaneous stimulation of the abdominal wall, ear, and ankle at a frequency of 20 Hz decreased the number of bladder contractions during infusion with acetic acid. As revealed by a comparison of various stimulation frequencies of the tibial nerve during bladder infusion with acetic acid, the duration of contraction was significantly shorter during stimulation at 1 kHz and 3 kHz relative to stimulation at 20 Hz (P=0.025 and P=0.044, respectively). Conclusions: The application of transcutaneous electrical stimulation to the abdominal wall, ear, and tibial nerve could provide less invasive and more cost-effective treatment options for OAB relative to percutaneous tibial nerve stimulation and sacral neuromodulation. A follow-up study involving a larger sample size is recommended.