The Experts below are selected from a list of 8616 Experts worldwide ranked by ideXlab platform
H. Harry Asada - One of the best experts on this subject based on the ideXlab platform.
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Leveraging Natural Load Dynamics With Variable Gear-Ratio Actuators
IEEE Robotics and Automation Letters, 2017Co-Authors: Alexandre Girard, H. Harry AsadaAbstract:This paper presents a robotic system where the Gear-Ratio of an actuator is dynamically changed to either leverage or attenuate the natural load dynamics. Based on this principle, lightweight robotic systems can be made fast and strong; exploiting the natural load dynamics for moving at higher speeds (small reduction Ratio), while also able to bear a large load through the attenuation of the load dynamics (large reduction Ratio). A model-based control algorithm to automatically select the optimal Gear-Ratios that minimize the total actuator torques for an arbitrary dynamic state and expected uncertainty level is proposed. Also, a novel 3-DoF robot arm using custom actuators with two discrete Gear-Ratios is presented. The advantages of Gear-shifting dynamically are demonstrated through experiments and simulations. Results show that actively changing the Gear-Ratio using the proposed control algorithms can lead to an order-of-magnitude reduction of necessary actuator torque and power, and also increase robustness to disturbances.
Mehran Mehregany - One of the best experts on this subject based on the ideXlab platform.
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Effect of rotor slip on the Gear Ratio of harmonic side-drive micromotors
Sensors and Actuators A: Physical, 1993Co-Authors: S.m. Phillips, Mehran MehreganyAbstract:Abstract This paper presents a preliminary model of the Gear Ratio of center-pin bearing harmonic (or wobble) side-drive micromotors, accounting for finite friction in the bearing and at the bushing contacts. The Gear Ratio of a wobble micromotor is affected by rotor slip, which is a function of motive torque, excitation angle, and friction torque. The Gear Ratio of a wobble micromotor can be expressed as a constant term plus a term that accounts for rotor slip. The constant term is the ideal or nominal Gear Ratio and is equal to the bearing radius divided by the bearing clearance. The rotor-slip term is shown to be directly proportional to the bushing friction torque and inversely proportional to the square of the excitation voltage. The derived model is used to study the opeRation of wobble micromotors in nitrogen through Gear-Ratio measurements. The model fit of the experimental results is within 10%.
Zhengchao Xie - One of the best experts on this subject based on the ideXlab platform.
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multi objective sliding mode control on vehicle cornering stability with variable Gear Ratio actuator based active front steering systems
Sensors, 2016Co-Authors: Pak Kin Wong, Jing Zhao, Zhengchao XieAbstract:Active front steering (AFS) is an emerging technology to improve the vehicle cornering stability by introducing an additional small steering angle to the driver’s input. This paper proposes an AFS system with a variable Gear Ratio steering (VGRS) actuator which is controlled by using the sliding mode control (SMC) strategy to improve the cornering stability of vehicles. In the design of an AFS system, different sensors are considered to measure the vehicle state, and the mechanism of the AFS system is also modelled in detail. Moreover, in order to improve the cornering stability of vehicles, two dependent objectives, namely sideslip angle and yaw rate, are considered together in the design of SMC strategy. By evaluating the cornering performance, Sine with Dwell and accident avoidance tests are conducted, and the simulation results indicate that the proposed SMC strategy is capable of improving the cornering stability of vehicles in practice.
Masayoshi Tomizuka - One of the best experts on this subject based on the ideXlab platform.
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Control Design for Cancellation of Unnatural Reaction Torque and VibRations in Variable-Gear-Ratio Steering System
Volume 1: Aerial Vehicles; Aerospace Control; Alternative Energy; Automotive Control Systems; Battery Systems; Beams and Flexible Structures; Biologic, 2013Co-Authors: Atsushi Oshima, Sumio Sugita, Xu Chen, Masayoshi TomizukaAbstract:Variable-Gear-Ratio steering is an advanced feature in automotive vehicles. As the name suggest, it changes the steering Gear Ratio depending on the speed of the vehicle. This feature can simplify steering for the driver, which leads to various advantages, such as improved vehicle comfort, stability, and safety. One serious problem, however, is that the variable-Gear-Ratio system generates unnatural torque to the driver whenever the variable-Gear-Ratio control is activated. Such unnatural torque includes both low-frequency and steering-speed-dependent components. This paper proposes a control method to cancel this unnatural torque. We address the problem by using a tire sensor and a set of feedback and feedforward algorithms. Effectiveness of the proposed method is experimentally verified using a hardware-in-the-loop experimental setup. Stability and robustness under model uncertainties are evaluated.Copyright © 2013 by ASME
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Cancellation of Unnatural Reaction Torque in Variable-Gear-Ratio
Journal of Dynamic Systems Measurement and Control, 2012Co-Authors: Sumio Sugita, Masayoshi TomizukaAbstract:Variable-Gear-Ratio steering, also known as active steering, is an advanced steering technology which enhances the driver’s comfort and vehicle operability. However, one big problem, namely the unnatural reaction torque created by the variable actuator, restricts the further practical-use of the variable-Gear-Ratio steering. This paper proposes a control method to cancel the unnatural torque using a simple concept called friction relocation. Effectiveness of the method is experimentally confirmed using a hardware-in-the-loop simulator.
Zi-qiang Zhu - One of the best experts on this subject based on the ideXlab platform.
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Influence of Gear Ratio on the Performance of Fractional Slot Concentrated Winding Permanent Magnet Machines
IEEE Transactions on Industrial Electronics, 2019Co-Authors: Yue Liu, Zi-qiang ZhuAbstract:Fractional slot concentrated winding (FSCW) permanent magnet synchronous machines (PMSMs) have been a research hotspot over the past few decades. Recently, the magnetic Gearing effect in FSCW PMSMs is revealed along with its Gear Ratio, which is a function of slot/pole number combination. At the design stage of FSCW PMSMs, one of the key issues is the selection of the slot/pole number combination. This paper shows that the Gear Ratio can contribute to a proper slot/pole number selection in any multiphase FSCW PMSMs by acting as a unified index for a quick overall performance comparison. In this paper, first, the magnetic Gearing effect in FSCW PMSMs is explained and the Gear Ratio is further discussed. The advantages of adopting Gear Ratio as the overall performance index over other indices are revealed. The influence of the Gear Ratio on the winding factor, torque output, cogging torque, inductance, and rotor losses of three- and six-phase FSCW PMSMs is analyzed and validated by experiments, thus proving the analyses.
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Influence of Gear Ratio on electromagnetic performance and geometries of vernier permanent magnet synchronous machines
2017 IEEE Energy Conversion Congress and Exposition (ECCE), 2017Co-Authors: Yue Liu, Zi-qiang ZhuAbstract:Vernier permanent magnet synchronous machine (VPMSM) is a promising candidate for low speed direct-drive applications. At the design stage of VPMSMs, one of the key issues is the selection of the slot/pole number combination. This paper will show that a proper selection of the slot/pole number combination can be achieved based on an index parameter of VPMSMs: the Gear Ratio. Firstly, the magnetic Gearing effect and the expression of the Gear Ratio in the VPMSM are introduced. The VPMSMs with different slot/pole number combinations are selected and globally optimized for investigation. Then, the influence of the Gear Ratio on flux linkage, back EMF, cogging torque, output torque, inductance, power factor, losses and machine geometries are investigated. The results show that the Gear Ratio can be used as a reference for performance comparison. Furthermore, it can serve as a guideline for selecting the appropriate slot/pole combination at the machine design stage.
