The Experts below are selected from a list of 1872 Experts worldwide ranked by ideXlab platform
Roberto Cárdenas - One of the best experts on this subject based on the ideXlab platform.
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Model Predictive Torque Control for Torque Ripple Compensation in Variable-Speed PMSMs
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Andrés Mora, Álvaro Orellana, Jorge Juliet, Roberto CárdenasAbstract:This paper presents a new and simple finite-control set model predictive control strategy to reduce the torque ripple in permanent-magnet synchronous machines (PMSMs). The method is based on minimizing a cost function that considers the flux linkage torque harmonics obtained from a discrete-time model of the machine. The power converter switching state that minimizes this cost function is selected and applied during a whole sampling period. Additionally, it is proposed to mitigate the other source of torque ripple, known as cogging-torque, using a feed-Forward Signal applied to the torque control loop. A hybrid method that uses the output information from an observer and look-up table is presented to obtain a good cogging-torque estimation and thus an accurate mitigation of this disturbance torque at low rotational speed. Experimental results demonstrate the good performance of the torque ripple compensation methods presented in this paper.
Xinbo Qi - One of the best experts on this subject based on the ideXlab platform.
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An Improved Sliding Mode Control Using Disturbance Torque Observer for Permanent Magnet Synchronous Motor
IEEE Access, 2019Co-Authors: Qi Wang, Haitao Yu, Min Wang, Xinbo QiAbstract:For the purpose of optimizing the speed control performance of the permanent magnet synchronous motor (PMSM) system, an adaptive sliding mode control (SMC) approach combining disturbance torque observer (DTO) is proposed during this paper. First, an improved sliding mode reaching law (SMRL) is introduced to reduce the sliding mode chattering. According to the choice of piecewise function term, the proposed SMRL adaptively selects the reaching velocity of the sliding mode. Then, the DTO is proposed to compensate for the effect of external disturbances. The DTO is used to produce a feed-Forward Signal, which is applied to the speed control loop, and the proposed SMRL is proved by Lyapunov law to ensure the stability of the whole system. Finally, the simulation and experiment results are implemented in Matlab2018a and TMS320F28335 (TI company's digital Signal processor, DSP), respectively. The simulation and experimental results indicate the availability of the proposed SMC approach.
Henry M Kronenberg - One of the best experts on this subject based on the ideXlab platform.
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resting zone of the growth plate houses a unique class of skeletal stem cells
Nature, 2018Co-Authors: Koji Mizuhashi, Yuki Matsushita, Naoko Sakagami, Akira Takahashi, Thomas L Saunders, Takashi Nagasawa, Henry M KronenbergAbstract:Skeletal stem cells regulate bone growth and homeostasis by generating diverse cell types, including chondrocytes, osteoblasts and marrow stromal cells. The emerging concept postulates that there exists a distinct type of skeletal stem cell that is closely associated with the growth plate1–4, which is a type of cartilaginous tissue that has critical roles in bone elongation5. The resting zone maintains the growth plate by expressing parathyroid hormone-related protein (PTHrP), which interacts with Indian hedgehog (Ihh) that is released from the hypertrophic zone6–10, and provides a source of other chondrocytes11. However, the identity of skeletal stem cells and how they are maintained in the growth plate are unknown. Here we show, in a mouse model, that skeletal stem cells are formed among PTHrP-positive chondrocytes within the resting zone of the postnatal growth plate. PTHrP-positive chondrocytes expressed a panel of markers for skeletal stem and progenitor cells, and uniquely possessed the properties of skeletal stem cells in cultured conditions. Cell-lineage analysis revealed that PTHrP-positive chondrocytes in the resting zone continued to form columnar chondrocytes in the long term; these chondrocytes underwent hypertrophy, and became osteoblasts and marrow stromal cells beneath the growth plate. Transit-amplifying chondrocytes in the proliferating zone—which was concertedly maintained by a Forward Signal from undifferentiated cells (PTHrP) and a reverse Signal from hypertrophic cells (Ihh)—provided instructive cues to maintain the cell fates of PTHrP-positive chondrocytes in the resting zone. Our findings unravel a type of somatic stem cell that is initially unipotent and acquires multipotency at the post-mitotic stage, underscoring the malleable nature of the skeletal cell lineage. This system provides a model in which functionally dedicated stem cells and their niches are specified postnatally, and maintained throughout tissue growth by a tight feedback regulation system. In a mouse model, PTHrP-positive chondrocytes in the resting zone of the growth plate constitute a unique stem-cell population, which is initially unipotent and makes columnar chondrocytes that later exhibit multipotency.
Oleg Ivlev - One of the best experts on this subject based on the ideXlab platform.
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Adaptive position control of fluidic soft-robots working with unknown loads
2013 IEEE ASME International Conference on Advanced Intelligent Mechatronics, 2013Co-Authors: Javad Taghia, Andre Wilkening, Oleg IvlevAbstract:The compliance of robot structure is essential to provide safety if robots are working in the direct contact with humans. Soft-actuators possess natural inherent compliance but they are characterized with highly non-linear dynamics making accurate control a challenging task. This paper presents the robust and adaptive position control of soft-robots based on pneumatic actuators with rotary elastic chambers (REC-actuators). Previous work shows that accurate control of soft-robots is possible if load parameters are known and taken into account in quasi-static model of soft-robots, that is used as feed-Forward Signal. This paper demonstrates that adaptation of the robot model provides flexibility and robustness when soft-robots deal with unknown loads. It is shown that due to adaptation the load parameters are not needed to be changed in the quasi-static robot model. The performance of the adaptive controller is proven in simulation and in experiments using firstly a simple 1 degree of freedom (DoF) and then a complex 6 DoF robot structure.
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Position Control of Soft-Robots with Rotary-Type Pneumatic Actuators
ROBOTIK 2012; 7th German Conference on Robotics, 2012Co-Authors: Javad Taghia, Andre Wilkening, Oleg IvlevAbstract:The objective of this work is the development and evaluation of a non-linear control concept for pneumatic soft-robots based on direct acting actuators of rotary-type (REC-actuators). Providing lightweight and inherent compliance, pneumatic soft-actuators are very suitable to construct service and rehabilitation robots, intended to work in direct contact with humans. However, an accurate and robust control of such robots is a challenging task, due to their high non-linear dynamics, especially for robots with a number of rotary joints. In this paper the usability of a decentralized joint position control scheme is experimentally investigated for soft-robots with two different kinematics, containing 4 and 6 REC-actuators respectively. It is shown, that complemented with active gravity compensation, based on the quasi-static robot model as feed-Forward Signal, the decentralized control scheme can be successfully applied to achieve robust joint space position control of soft-robots.
Andrés Mora - One of the best experts on this subject based on the ideXlab platform.
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Model Predictive Torque Control for Torque Ripple Compensation in Variable-Speed PMSMs
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Andrés Mora, Álvaro Orellana, Jorge Juliet, Roberto CárdenasAbstract:This paper presents a new and simple finite-control set model predictive control strategy to reduce the torque ripple in permanent-magnet synchronous machines (PMSMs). The method is based on minimizing a cost function that considers the flux linkage torque harmonics obtained from a discrete-time model of the machine. The power converter switching state that minimizes this cost function is selected and applied during a whole sampling period. Additionally, it is proposed to mitigate the other source of torque ripple, known as cogging-torque, using a feed-Forward Signal applied to the torque control loop. A hybrid method that uses the output information from an observer and look-up table is presented to obtain a good cogging-torque estimation and thus an accurate mitigation of this disturbance torque at low rotational speed. Experimental results demonstrate the good performance of the torque ripple compensation methods presented in this paper.