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In order to exert large force on an environment, it is effective to apply impulsive force. We describe the motions that perform tasks by applying impulsive force as “impact motion.” The objective of an impact motion is to exert large force on an environment, however if the impulsive force is too large, the robot may fall down due to the reaction force. This paper presents an optimization scheme to...
Computation of contact forces is essential for the simulation of mechanical systems with unilateral constraints, like bipedal robots. Most methods are based on the rigid body assumption. They can be categorized into constraint-based and penalty-based approaches. In the former, contact forces are computed by solving an optimization problem based on linear or nonlinear complementarity conditions. Unfortunately,...
The this work deals with neural network-based gait-pattern adaptation algorithms for an active lower limbs orthosis. Stable trajectories are generated during the optimization process, considering a stable trajectory generator based on the Zero Moment Point criterion and the inverse dynamic model. Additionally, two neural network (NN) are used to decrease the time-consuming computation of the model...
This paper presents the mechanical design of an ankle rehabilitation robotic device based on a 2-dof, redundantly actuated parallel mechanism. The parallel mechanism introduced in this paper has the advantage of mechanical and kinematic simplicity when compared to existing platforms while at the same time it is fully capable of carrying out all the exercises required by ankle rehabilitation protocols...
We consider the task of planning smooth trajectories for robot motion. In this paper we make two contributions. First we present a method for cubic spline optimization; this technique lets us simultaneously plan optimal task-space trajectories and fit cubic splines to the trajectories, while obeying many of the same constraints imposed by a typical motion planning algorithm. The method uses convex...
The design process of a powered robotic ankle prosthesis presents many obstacles that must be overcome. To be practically implemented, such a mechanism must not only run on batteries, but sustain a long running time between recharging. Using springs to passively and actively store and supply energy to the robotic ankle, small DC motors can be optimized to perform high peak power tasks without sacrificing...
The paper presents a novel method which generates hopping gaits for an articulated single leg. Inspired by human running, the flight phase is assumed to be nearly-passive. Consequently, the initial joint velocities of the flight phase can be solved by using a static optimization procedure, provided that the boundary joint angles have been picked in advance. The two hopping phases can then be dynamically...
This paper presents a novel approach which generates running gaits for a bipedal robot model. Inspired by human running, we assume that the flight phase is nearly-passive. Thus, the initial and final joint velocities follow from a static optimization procedure, provided that the boundary joint angles have been picked in advance. Dynamic optimization then produces the two running phases, with a simple...
We present a method to optimize the walking pattern of a humanoid robot for forward speed using suitable metaheuristics. Our starting point is a hand-tuned open-loop gait that we enhance with two feedback control mechanisms. First, we employ a P-controller that regulates the foot angle in order to reduce angular velocity of the robot's body. Second, we introduce a phase resetting mechanism that starts...
In this paper, we present a recursive method for the optimization of humanoid robot motions. The method is based on an efficient dynamics algorithm, which allows the calculation of the gradient function with respect to the control parameters analytically. The algorithm makes use of the theory of Lie groups and Lie algebra. The main objective of this method is to smooth the pre-calculated humanoid...
Nature has developed methods for controlling the movements of organisms with many degrees of freedom which differ strongly from existing approaches for balance control in humanoid robots: Biological organisms employ kinematic synergies that simultaneously engage many joints, and which are apparently designed in such a way that their superposition is approximately linear. We show in this article that...
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