Browsing by Author "Agrawal, Sunil K."

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Gait Analysis for a Human with a Robot Walking Helper
(2013)
Ko, Chun-Hsu
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Young, Kuu-Young
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Agrawal, Sunil K.
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電機工程學系
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Department of Electrical and Computer Engineering
With the growth of elderly population in our society, intelligent walking aids will play an important role in providing functional mobility to humans. In this paper, we propose a model to compute gait of humans walking with a robot helper. This model is aimed at designing a control system for the robot walking helper. The human model includes both the single support phase and impacts. Since a human will be walking along with the robot with its help, geometrical constraints and interaction forces are included. To achieve stable walking, zero moment point (ZMP) is utilized in the analysis and friction constraint is included within the reaction force from the ground. Simulations are performed to obtain optimal gait trajectories, the human applied joint torques, and the supporting forces from the robot walking helper.
Motion Guidance for a Passive Robot Walking Helper via User\'s Applied Hand Forces
(2016-12)
Hsieh, Yi-Hung
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Huang, Yi-Che
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Young, Kuu-Young
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Ko, Chun-Hsu
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Agrawal, Sunil K.
As the elderly population is rapidly growing in our society, robot walking helpers are receiving more attention these days. To be practical and safe for use in daily life, an important issue is whether these robot walking helpers can be effectively maneuvered and provide guidance to the users. These concerns become even more important for a passive robot walking helper, as it relies mainly on the user\'s applied forces to move. In this paper, we propose a motion guidance system for a passive robot walking helper. More specifically, we develop a system to identify user\'s intentions from applied grip forces. This system consists of a pair of force-sensing grips attached to the handles of the robot walking helper and a learning scheme for themapping between the measured grip forces and the driving force/torque imposed on the helper. The learning scheme, combined with an assistive strategy extended from our previous work, provides motion guidance to the elders during walking. The feasibility of the proposed system is demonstrated via a series of experiments involving motion assistance with i-Go, a passive robot walking helper developed in our laboratory.
Receding Horizon Passive Control for a Walk-Assist Robot
(2012)
Ko, Chun-Hsu
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Young, Kuu-Young
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Agrawal, Sunil K.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Passive walk-assist robots play an important role in providing safe mobility to the elderly. They use the brake torques on the wheels to assist the user walking and differentially steer the vehicle, while the user pushes the walker. It is important to appropriately select the brake torques in accordance with user-applied forces for controlling the robot. In this paper, a receding horizon passive control method is presented to calculate the brake torques so that the robot can perform point-to-point guidance. The control scheme first designs a smooth path to be followed by the robot. The terminal-state penalty is added to the cost function for path following, while the end point equality constraint is used to achieve the goal when the robot approaches the end point. The passivity of the system is guaranteed by adding the brake torque constraints into the formulated optimization problem. To be efficient, we look for a suboptimal solution of the optimization problem by using an analytical method. Simulation results show that the passive walk-assist robot, along with the proposed control scheme, can guide the user to a goal effectively.
Walk-Assist Robot: A Novel Approach to Gain Selection of a Braking Controller Using Differential Flatness
(2013-11-01)
Ko, Chun-Hsu
;
Young, Kuu-Young
;
Huang, Yi-Che
;
Agrawal, Sunil K.
;
電機工程學系
With increasing populations of the elderly in our society, robot technology will play an important role in providing functional mobility to humans. From the perspective of human safety, it is desirable that controllers for walk-assist robots be dissipative, i.e., the energy is supplied from the human to the walker, while the controller modulates this energy. The simplest form of a dissipating controller is a brake, where resistive torques are applied to the wheels proportional to their speeds. The fundamental question that we ask in this brief is how to modulate these proportional gains over time for the two wheels so that the walker can perform point-to-point motions. The unique contribution of this brief is a novel way in which the theory of differential flatness is used to plan the trajectory of these braking gains. Since the user input forces are not known a priori, the trajectory of the braking gain is computed iteratively during the motion. Simulation and experimental results show that the walk-assist robot, along with the structure of this proposed control scheme, can guide the user to reach the goal.